Nested Loops - Python Programming

You're printing a 10×10 multiplication table. For each row (1-10), you need to print 10 products (row × 1, row × 2, ... row × 10). The outer loop picks the row; the inner loop fills each column.

Multiplication table

Generate a multiplication table using nested loops.

                            size
                            size = 5 (default)size = 3size = 10
                        

                            multiplication.py
                        
Replay: real traced execution (multi-file project)

                            size = 5

# Print header
print("   ", end="")
for i in range(1, size + 1):
    print(f"{i:4d}", end="")
print()
print("   " + "-" * (size * 4))

# Print table
for row in range(1, size + 1):
    print(f"{row:2d} |", end="")
    for col in range(1, size + 1):
        print(f"{row * col:4d}", end="")
    print()


size = 3

# Print header
print("   ", end="")
for i in range(1, size + 1):
    print(f"{i:4d}", end="")
print()
print("   " + "-" * (size * 4))

# Print table
for row in range(1, size + 1):
    print(f"{row:2d} |", end="")
    for col in range(1, size + 1):
        print(f"{row * col:4d}", end="")
    print()


size = 10

# Print header
print("   ", end="")
for i in range(1, size + 1):
    print(f"{i:4d}", end="")
print()
print("   " + "-" * (size * 4))

# Print table
for row in range(1, size + 1):
    print(f"{row:2d} |", end="")
    for col in range(1, size + 1):
        print(f"{row * col:4d}", end="")
    print()



                        
1size ← 51size→ 5 = 5  #@size=3, 1023# Print header4print("   ", end="")5for i in range(1, size + 1):⋯output   
2for i in range(1, size + 1):pass 1 of 5⋯4print("   ", end="")5for i1 in range(1, size5 + 1):6    print(f"{i1:4d}", end="")7print()⋯output   1All 5 passes — pass 1 is the card abovepassi
11
22
33
44
55
3print("   " + "-" * (size * 4))⋯6    print(f"{i:4d}", end="")7print()8print("   " + "-" * (size5 * 4))⋯output   --------------------
4for row in range(1, size + 1):  #?outer_looppass 1 of 5⋯10# Print table11for row1 in range(1, size5 + 1):  #?outer_loop12    print(f"{row1:2d} |", end="")13    for col in range(1, size + 1):  #?inner_loop⋯output 1 |All 5 passes — pass 1 is the card abovepassrow
11
22
33
44
55
5for col in range(1, size + 1):  #?inner_looppass 1 of 25⋯12print(f"{row:2d} |", end="")13for col1 in range(1, size5 + 1):  #?inner_loop14    print(f"{row1 * col1:4d}", end="")15print()⋯output   125 passes — pass 1 is the card abovepasscolrow
111
221
331
441
551
612
722
832
942
⋯ 14 more passes ⋯
2445
2555
6print()⋯14    print(f"{row * col:4d}", end="")15print()⋯
7print()⋯14    print(f"{row * col:4d}", end="")15print()⋯
8print()⋯14    print(f"{row * col:4d}", end="")15print()⋯
9print()⋯14    print(f"{row * col:4d}", end="")15print()⋯
10print()⋯14    print(f"{row * col:4d}", end="")15print()⋯
1size ← 31size→ 3 = 323# Print header4print("   ", end="")5for i in range(1, size + 1):⋯output   
2for i in range(1, size + 1):pass 1 of 3⋯4print("   ", end="")5for i1 in range(1, size3 + 1):6    print(f"{i1:4d}", end="")7print()⋯output   1All 3 passes — pass 1 is the card abovepassi
11
22
33
3print("   " + "-" * (size * 4))⋯6    print(f"{i:4d}", end="")7print()8print("   " + "-" * (size3 * 4))⋯output   ------------
4for row in range(1, size + 1):pass 1 of 3⋯10# Print table11for row1 in range(1, size3 + 1):12    print(f"{row1:2d} |", end="")13    for col in range(1, size + 1):⋯output 1 |All 3 passes — pass 1 is the card abovepassrow
11
22
33
5for col in range(1, size + 1):pass 1 of 9⋯12print(f"{row:2d} |", end="")13for col1 in range(1, size3 + 1):14    print(f"{row1 * col1:4d}", end="")15print()⋯output   1All 9 passes — pass 1 is the card abovepasscolrow
111
221
331
412
522
632
713
823
933
6print()⋯14    print(f"{row * col:4d}", end="")15print()⋯
7print()⋯14    print(f"{row * col:4d}", end="")15print()⋯
8print()⋯14    print(f"{row * col:4d}", end="")15print()⋯
1size ← 101size→ 10 = 1023# Print header4print("   ", end="")5for i in range(1, size + 1):⋯output   
2for i in range(1, size + 1):pass 1 of 10⋯4print("   ", end="")5for i1 in range(1, size10 + 1):6    print(f"{i1:4d}", end="")7print()⋯output   1All 10 passes — pass 1 is the card abovepassi
11
22
33
44
55
66
77
88
99
1010
3print("   " + "-" * (size * 4))⋯6    print(f"{i:4d}", end="")7print()8print("   " + "-" * (size10 * 4))⋯output   ----------------------------------------
4for row in range(1, size + 1):pass 1 of 10⋯10# Print table11for row1 in range(1, size10 + 1):12    print(f"{row1:2d} |", end="")13    for col in range(1, size + 1):⋯output 1 |All 10 passes — pass 1 is the card abovepassrow
11
22
33
44
55
66
77
88
99
1010
5for col in range(1, size + 1):pass 1 of 100⋯12print(f"{row:2d} |", end="")13for col1 in range(1, size10 + 1):14    print(f"{row1 * col1:4d}", end="")15print()⋯output   1100 passes — pass 1 is the card abovepasscolrow
111
221
331
441
551
661
771
881
991
⋯ 89 more passes ⋯
99910
1001010
6print()⋯14    print(f"{row * col:4d}", end="")15print()⋯
7print()⋯14    print(f"{row * col:4d}", end="")15print()⋯
8print()⋯14    print(f"{row * col:4d}", end="")15print()⋯
9print()⋯14    print(f"{row * col:4d}", end="")15print()⋯
10print()⋯14    print(f"{row * col:4d}", end="")15print()⋯
11print()⋯14    print(f"{row * col:4d}", end="")15print()⋯
12print()⋯14    print(f"{row * col:4d}", end="")15print()⋯
13print()⋯14    print(f"{row * col:4d}", end="")15print()⋯
14print()⋯14    print(f"{row * col:4d}", end="")15print()⋯
15print()⋯14    print(f"{row * col:4d}", end="")15print()⋯

All 5 passes — pass 1 is the card above
pass	`i`
1	1
2	2
3	3
4	4
5	5

All 5 passes — pass 1 is the card above
pass	`row`
1	1
2	2
3	3
4	4
5	5

25 passes — pass 1 is the card above
pass	`col`	`row`
1	1	1
2	2	1
3	3	1
4	4	1
5	5	1
6	1	2
7	2	2
8	3	2
9	4	2
⋯ 14 more passes ⋯
24	4	5
25	5	5

All 3 passes — pass 1 is the card above
pass	`i`
1	1
2	2
3	3

All 3 passes — pass 1 is the card above
pass	`row`
1	1
2	2
3	3

All 9 passes — pass 1 is the card above
pass	`col`	`row`
1	1	1
2	2	1
3	3	1
4	1	2
5	2	2
6	3	2
7	1	3
8	2	3
9	3	3

All 10 passes — pass 1 is the card above
pass	`i`
1	1
2	2
3	3
4	4
5	5
6	6
7	7
8	8
9	9
10	10

All 10 passes — pass 1 is the card above
pass	`row`
1	1
2	2
3	3
4	4
5	5
6	6
7	7
8	8
9	9
10	10

100 passes — pass 1 is the card above
pass	`col`	`row`
1	1	1
2	2	1
3	3	1
4	4	1
5	5	1
6	6	1
7	7	1
8	8	1
9	9	1
⋯ 89 more passes ⋯
99	9	10
100	10	10

Outer loop: each row (1-10). Inner loop: each column (multiply by 1-10).

nested loop A loop inside another loop. Inner completes fully for each outer iteration.

Print rectangle of stars

Draw a rectangle pattern with asterisks.

                            example
                            width = 5, height = 3 (default)width = 3width = 8height = 2height = 5
                        

                            rectangle.py
                        
Replay: real traced execution (multi-file project)

                            width = 5
height = 3

print(f"Rectangle {width}x{height}:")

for row in range(height):
    for col in range(width):
        print("* ", end="")
    print()  # New line after each row

# Hollow rectangle
print("\nHollow rectangle:")
for row in range(height):
    for col in range(width):
        if row == 0 or row == height - 1 or col == 0 or col == width - 1:
            print("* ", end="")
        else:
            print("  ", end="")
    print()

# Pythonic: string multiplication
print("\nUsing string multiplication:")
for row in range(height):
    print("* " * width)
width = 3
height = 3

print(f"Rectangle {width}x{height}:")

for row in range(height):
    for col in range(width):
        print("* ", end="")
    print()  # New line after each row

# Hollow rectangle
print("\nHollow rectangle:")
for row in range(height):
    for col in range(width):
        if row == 0 or row == height - 1 or col == 0 or col == width - 1:
            print("* ", end="")
        else:
            print("  ", end="")
    print()

# Pythonic: string multiplication
print("\nUsing string multiplication:")
for row in range(height):
    print("* " * width)
width = 8
height = 3

print(f"Rectangle {width}x{height}:")

for row in range(height):
    for col in range(width):
        print("* ", end="")
    print()  # New line after each row

# Hollow rectangle
print("\nHollow rectangle:")
for row in range(height):
    for col in range(width):
        if row == 0 or row == height - 1 or col == 0 or col == width - 1:
            print("* ", end="")
        else:
            print("  ", end="")
    print()

# Pythonic: string multiplication
print("\nUsing string multiplication:")
for row in range(height):
    print("* " * width)
width = 5
height = 2

print(f"Rectangle {width}x{height}:")

for row in range(height):
    for col in range(width):
        print("* ", end="")
    print()  # New line after each row

# Hollow rectangle
print("\nHollow rectangle:")
for row in range(height):
    for col in range(width):
        if row == 0 or row == height - 1 or col == 0 or col == width - 1:
            print("* ", end="")
        else:
            print("  ", end="")
    print()

# Pythonic: string multiplication
print("\nUsing string multiplication:")
for row in range(height):
    print("* " * width)
width = 5
height = 5

print(f"Rectangle {width}x{height}:")

for row in range(height):
    for col in range(width):
        print("* ", end="")
    print()  # New line after each row

# Hollow rectangle
print("\nHollow rectangle:")
for row in range(height):
    for col in range(width):
        if row == 0 or row == height - 1 or col == 0 or col == width - 1:
            print("* ", end="")
        else:
            print("  ", end="")
    print()

# Pythonic: string multiplication
print("\nUsing string multiplication:")
for row in range(height):
    print("* " * width)

                        
1width ← 5, height ← 31width→ 5 = 5   #@width=3, 82height→ 3 = 3  #@height=2, 534print(f"Rectangle {width5}x{height3}:")⋯outputRectangle 5x3:
2for row in range(height):pass 1 of 3⋯6for row0 in range(height3):7    for col in range(width):8        print("* ", end="")⋯All 3 passes — pass 1 is the card abovepassrow
10
21
32
3for col in range(width):pass 1 of 15⋯6for row in range(height):7    for col0 in range(width5):8        print("* ", end="")9    print()  # New line after each row⋯output* 15 passes — pass 1 is the card abovepasscol
10
21
32
43
54
60
71
82
93
⋯ 4 more passes ⋯
143
154
4print()  # New line after each row⋯8    print("* ", end="")9print()  # New line after each row⋯
5print()  # New line after each row⋯8    print("* ", end="")9print()  # New line after each row⋯
6print()  # New line after each row⋯8    print("* ", end="")9print()  # New line after each row⋯
7print(" Hollow rectangle:")⋯11# Hollow rectangle12print("\nHollow rectangle:")13for row in range(height):⋯output
Hollow rectangle:
8for row in range(height):pass 1 of 3⋯12print("\nHollow rectangle:")13for row0 in range(height3):14    for col in range(width):15        if row == 0 or row == height - 1 or col == 0 or col == width - 1:⋯All 3 passes — pass 1 is the card abovepassrow
10
21
32
9for col in range(width):pass 1 of 15⋯13for row in range(height):14    for col0 in range(width5):15        if row == 0 or row == height - 1 or col == 0 or col == width - 1:16            print("* ", end="")⋯15 passes — pass 1 is the card abovepasscol
10
21
32
43
54
60
71
82
93
⋯ 4 more passes ⋯
143
154
10if row == 0 or row == height - 1 or col == 0 or col == width - 1:pass 1 of 12⋯14for col in range(width):15    if row0 == 0 or row == height3 - 1 or col0 == 0 or col == width5 - 1:16        print("* ", end="")17    else:⋯output* All 12 passes — pass 1 is the card abovepassrowcol
100
201
302
403
504
610
714
820
921
1022
1123
1224
11print()⋯18        print("  ", end="")19print()⋯
12else:pass 1 of 3⋯15    if row == 0 or row == height - 1 or col == 0 or col == width - 1:16        print("* ", end="")17    else:18        print("  ", end="")19print()⋯output  
13print()⋯18        print("  ", end="")19print()⋯
14print()⋯18        print("  ", end="")19print()⋯
15print(" Using string multiplication:")⋯21# Pythonic: string multiplication22print("\nUsing string multiplication:")23for row in range(height):⋯output
Using string multiplication:
16for row in range(height):pass 1 of 3⋯22print("\nUsing string multiplication:")23for row0 in range(height3):24    print("* " * width5)⋯output* * * * * All 3 passes — pass 1 is the card abovepassrow
10
21
32
1width ← 3, height ← 31width→ 3 = 32height→ 3 = 334print(f"Rectangle {width3}x{height3}:")⋯outputRectangle 3x3:
2for row in range(height):pass 1 of 3⋯6for row0 in range(height3):7    for col in range(width):8        print("* ", end="")⋯All 3 passes — pass 1 is the card abovepassrow
10
21
32
3for col in range(width):pass 1 of 9⋯6for row in range(height):7    for col0 in range(width3):8        print("* ", end="")9    print()  # New line after each row⋯output* All 9 passes — pass 1 is the card abovepasscol
10
21
32
40
51
62
70
81
92
4print()  # New line after each row⋯8    print("* ", end="")9print()  # New line after each row⋯
5print()  # New line after each row⋯8    print("* ", end="")9print()  # New line after each row⋯
6print()  # New line after each row⋯8    print("* ", end="")9print()  # New line after each row⋯
7print(" Hollow rectangle:")⋯11# Hollow rectangle12print("\nHollow rectangle:")13for row in range(height):⋯output
Hollow rectangle:
8for row in range(height):pass 1 of 3⋯12print("\nHollow rectangle:")13for row0 in range(height3):14    for col in range(width):15        if row == 0 or row == height - 1 or col == 0 or col == width - 1:⋯All 3 passes — pass 1 is the card abovepassrow
10
21
32
9for col in range(width):pass 1 of 9⋯13for row in range(height):14    for col0 in range(width3):15        if row == 0 or row == height - 1 or col == 0 or col == width - 1:16            print("* ", end="")⋯All 9 passes — pass 1 is the card abovepasscol
10
21
32
40
51
62
70
81
92
10if row == 0 or row == height - 1 or col == 0 or col == width - 1:pass 1 of 8⋯14for col in range(width):15    if row0 == 0 or row == height3 - 1 or col0 == 0 or col == width3 - 1:16        print("* ", end="")17    else:⋯output* All 8 passes — pass 1 is the card abovepassrowcol
100
201
302
410
512
620
721
822
11print()⋯18        print("  ", end="")19print()⋯
12else:⋯15    if row == 0 or row == height - 1 or col == 0 or col == width - 1:16        print("* ", end="")17    else:18        print("  ", end="")19print()⋯output  
13print()⋯18        print("  ", end="")19print()⋯
14print()⋯18        print("  ", end="")19print()⋯
15print(" Using string multiplication:")⋯21# Pythonic: string multiplication22print("\nUsing string multiplication:")23for row in range(height):⋯output
Using string multiplication:
16for row in range(height):pass 1 of 3⋯22print("\nUsing string multiplication:")23for row0 in range(height3):24    print("* " * width3)⋯output* * * All 3 passes — pass 1 is the card abovepassrow
10
21
32
1width ← 8, height ← 31width→ 8 = 82height→ 3 = 334print(f"Rectangle {width8}x{height3}:")⋯outputRectangle 8x3:
2for row in range(height):pass 1 of 3⋯6for row0 in range(height3):7    for col in range(width):8        print("* ", end="")⋯All 3 passes — pass 1 is the card abovepassrow
10
21
32
3for col in range(width):pass 1 of 24⋯6for row in range(height):7    for col0 in range(width8):8        print("* ", end="")9    print()  # New line after each row⋯output* 24 passes — pass 1 is the card abovepasscol
10
21
32
43
54
65
76
87
90
⋯ 13 more passes ⋯
236
247
4print()  # New line after each row⋯8    print("* ", end="")9print()  # New line after each row⋯
5print()  # New line after each row⋯8    print("* ", end="")9print()  # New line after each row⋯
6print()  # New line after each row⋯8    print("* ", end="")9print()  # New line after each row⋯
7print(" Hollow rectangle:")⋯11# Hollow rectangle12print("\nHollow rectangle:")13for row in range(height):⋯output
Hollow rectangle:
8for row in range(height):pass 1 of 3⋯12print("\nHollow rectangle:")13for row0 in range(height3):14    for col in range(width):15        if row == 0 or row == height - 1 or col == 0 or col == width - 1:⋯All 3 passes — pass 1 is the card abovepassrow
10
21
32
9for col in range(width):pass 1 of 24⋯13for row in range(height):14    for col0 in range(width8):15        if row == 0 or row == height - 1 or col == 0 or col == width - 1:16            print("* ", end="")⋯24 passes — pass 1 is the card abovepasscol
10
21
32
43
54
65
76
87
90
⋯ 13 more passes ⋯
236
247
10if row == 0 or row == height - 1 or col == 0 or col == width - 1:pass 1 of 18⋯14for col in range(width):15    if row0 == 0 or row == height3 - 1 or col0 == 0 or col == width8 - 1:16        print("* ", end="")17    else:⋯output* 18 passes — pass 1 is the card abovepassrowcol
100
201
302
403
504
605
706
807
910
⋯ 7 more passes ⋯
1726
1827
11print()⋯18        print("  ", end="")19print()⋯
12else:pass 1 of 6⋯15    if row == 0 or row == height - 1 or col == 0 or col == width - 1:16        print("* ", end="")17    else:18        print("  ", end="")19print()⋯output  
13print()⋯18        print("  ", end="")19print()⋯
14print()⋯18        print("  ", end="")19print()⋯
15print(" Using string multiplication:")⋯21# Pythonic: string multiplication22print("\nUsing string multiplication:")23for row in range(height):⋯output
Using string multiplication:
16for row in range(height):pass 1 of 3⋯22print("\nUsing string multiplication:")23for row0 in range(height3):24    print("* " * width8)⋯output* * * * * * * * All 3 passes — pass 1 is the card abovepassrow
10
21
32
1width ← 5, height ← 21width→ 5 = 52height→ 2 = 234print(f"Rectangle {width5}x{height2}:")⋯outputRectangle 5x2:
2for row in range(height):pass 1 of 2⋯6for row0 in range(height2):7    for col in range(width):8        print("* ", end="")⋯
3for col in range(width):pass 1 of 10⋯6for row in range(height):7    for col0 in range(width5):8        print("* ", end="")9    print()  # New line after each row⋯output* All 10 passes — pass 1 is the card abovepasscol
10
21
32
43
54
60
71
82
93
104
4print()  # New line after each row⋯8    print("* ", end="")9print()  # New line after each row⋯
5for row in range(height):pass 2 of 2⋯6for row1 in range(height2):7    for col in range(width):8        print("* ", end="")⋯
6print()  # New line after each row⋯8    print("* ", end="")9print()  # New line after each row⋯
7print(" Hollow rectangle:")⋯11# Hollow rectangle12print("\nHollow rectangle:")13for row in range(height):⋯output
Hollow rectangle:
8for row in range(height):pass 1 of 2⋯12print("\nHollow rectangle:")13for row0 in range(height2):14    for col in range(width):15        if row == 0 or row == height - 1 or col == 0 or col == width - 1:⋯
9for col in range(width):pass 1 of 10⋯13for row in range(height):14    for col0 in range(width5):15        if row == 0 or row == height - 1 or col == 0 or col == width - 1:16            print("* ", end="")⋯All 10 passes — pass 1 is the card abovepasscol
10
21
32
43
54
60
71
82
93
104
10if row == 0 or row == height - 1 or col == 0 or col == width - 1:pass 1 of 10⋯14for col in range(width):15    if row0 == 0 or row == height2 - 1 or col0 == 0 or col == width5 - 1:16        print("* ", end="")17    else:⋯output* All 10 passes — pass 1 is the card abovepassrowcol
100
201
302
403
504
610
711
812
913
1014
11print()⋯18        print("  ", end="")19print()⋯
12for row in range(height):pass 2 of 2⋯12print("\nHollow rectangle:")13for row1 in range(height2):14    for col in range(width):15        if row == 0 or row == height - 1 or col == 0 or col == width - 1:⋯
13print()⋯18        print("  ", end="")19print()⋯
14print(" Using string multiplication:")⋯21# Pythonic: string multiplication22print("\nUsing string multiplication:")23for row in range(height):⋯output
Using string multiplication:
15for row in range(height):pass 1 of 2⋯22print("\nUsing string multiplication:")23for row0 in range(height2):24    print("* " * width5)⋯output* * * * * 
16for row in range(height):pass 2 of 2⋯22print("\nUsing string multiplication:")23for row1 in range(height2):24    print("* " * width5)⋯output* * * * * 
1width ← 5, height ← 51width→ 5 = 52height→ 5 = 534print(f"Rectangle {width5}x{height5}:")⋯outputRectangle 5x5:
2for row in range(height):pass 1 of 5⋯6for row0 in range(height5):7    for col in range(width):8        print("* ", end="")⋯All 5 passes — pass 1 is the card abovepassrow
10
21
32
43
54
3for col in range(width):pass 1 of 25⋯6for row in range(height):7    for col0 in range(width5):8        print("* ", end="")9    print()  # New line after each row⋯output* 25 passes — pass 1 is the card abovepasscol
10
21
32
43
54
60
71
82
93
⋯ 14 more passes ⋯
243
254
4print()  # New line after each row⋯8    print("* ", end="")9print()  # New line after each row⋯
5print()  # New line after each row⋯8    print("* ", end="")9print()  # New line after each row⋯
6print()  # New line after each row⋯8    print("* ", end="")9print()  # New line after each row⋯
7print()  # New line after each row⋯8    print("* ", end="")9print()  # New line after each row⋯
8print()  # New line after each row⋯8    print("* ", end="")9print()  # New line after each row⋯
9print(" Hollow rectangle:")⋯11# Hollow rectangle12print("\nHollow rectangle:")13for row in range(height):⋯output
Hollow rectangle:
10for row in range(height):pass 1 of 5⋯12print("\nHollow rectangle:")13for row0 in range(height5):14    for col in range(width):15        if row == 0 or row == height - 1 or col == 0 or col == width - 1:⋯All 5 passes — pass 1 is the card abovepassrow
10
21
32
43
54
11for col in range(width):pass 1 of 25⋯13for row in range(height):14    for col0 in range(width5):15        if row == 0 or row == height - 1 or col == 0 or col == width - 1:16            print("* ", end="")⋯25 passes — pass 1 is the card abovepasscol
10
21
32
43
54
60
71
82
93
⋯ 14 more passes ⋯
243
254
12if row == 0 or row == height - 1 or col == 0 or col == width - 1:pass 1 of 16⋯14for col in range(width):15    if row0 == 0 or row == height5 - 1 or col0 == 0 or col == width5 - 1:16        print("* ", end="")17    else:⋯output* 16 passes — pass 1 is the card abovepassrowcol
100
201
302
403
504
610
714
820
924
⋯ 5 more passes ⋯
1543
1644
13print()⋯18        print("  ", end="")19print()⋯
14else:pass 1 of 9⋯15    if row == 0 or row == height - 1 or col == 0 or col == width - 1:16        print("* ", end="")17    else:18        print("  ", end="")19print()⋯output  
15print()⋯18        print("  ", end="")19print()⋯
16print()⋯18        print("  ", end="")19print()⋯
17print()⋯18        print("  ", end="")19print()⋯
18print()⋯18        print("  ", end="")19print()⋯
19print(" Using string multiplication:")⋯21# Pythonic: string multiplication22print("\nUsing string multiplication:")23for row in range(height):⋯output
Using string multiplication:
20for row in range(height):pass 1 of 5⋯22print("\nUsing string multiplication:")23for row0 in range(height5):24    print("* " * width5)⋯output* * * * * All 5 passes — pass 1 is the card abovepassrow
10
21
32
43
54

All 3 passes — pass 1 is the card above
pass	`row`
1	0
2	1
3	2

15 passes — pass 1 is the card above
pass	`col`
1	0
2	1
3	2
4	3
5	4
6	0
7	1
8	2
9	3
⋯ 4 more passes ⋯
14	3
15	4

All 3 passes — pass 1 is the card above
pass	`row`
1	0
2	1
3	2

15 passes — pass 1 is the card above
pass	`col`
1	0
2	1
3	2
4	3
5	4
6	0
7	1
8	2
9	3
⋯ 4 more passes ⋯
14	3
15	4

All 12 passes — pass 1 is the card above
pass	`row`	`col`
1	0	0
2	0	1
3	0	2
4	0	3
5	0	4
6	1	0
7	1	4
8	2	0
9	2	1
10	2	2
11	2	3
12	2	4

All 3 passes — pass 1 is the card above
pass	`row`
1	0
2	1
3	2

All 3 passes — pass 1 is the card above
pass	`row`
1	0
2	1
3	2

All 9 passes — pass 1 is the card above
pass	`col`
1	0
2	1
3	2
4	0
5	1
6	2
7	0
8	1
9	2

All 3 passes — pass 1 is the card above
pass	`row`
1	0
2	1
3	2

All 9 passes — pass 1 is the card above
pass	`col`
1	0
2	1
3	2
4	0
5	1
6	2
7	0
8	1
9	2

All 8 passes — pass 1 is the card above
pass	`row`	`col`
1	0	0
2	0	1
3	0	2
4	1	0
5	1	2
6	2	0
7	2	1
8	2	2

All 3 passes — pass 1 is the card above
pass	`row`
1	0
2	1
3	2

All 3 passes — pass 1 is the card above
pass	`row`
1	0
2	1
3	2

24 passes — pass 1 is the card above
pass	`col`
1	0
2	1
3	2
4	3
5	4
6	5
7	6
8	7
9	0
⋯ 13 more passes ⋯
23	6
24	7

All 3 passes — pass 1 is the card above
pass	`row`
1	0
2	1
3	2

24 passes — pass 1 is the card above
pass	`col`
1	0
2	1
3	2
4	3
5	4
6	5
7	6
8	7
9	0
⋯ 13 more passes ⋯
23	6
24	7

18 passes — pass 1 is the card above
pass	`row`	`col`
1	0	0
2	0	1
3	0	2
4	0	3
5	0	4
6	0	5
7	0	6
8	0	7
9	1	0
⋯ 7 more passes ⋯
17	2	6
18	2	7

All 3 passes — pass 1 is the card above
pass	`row`
1	0
2	1
3	2

All 10 passes — pass 1 is the card above
pass	`col`
1	0
2	1
3	2
4	3
5	4
6	0
7	1
8	2
9	3
10	4

All 10 passes — pass 1 is the card above
pass	`col`
1	0
2	1
3	2
4	3
5	4
6	0
7	1
8	2
9	3
10	4

All 10 passes — pass 1 is the card above
pass	`row`	`col`
1	0	0
2	0	1
3	0	2
4	0	3
5	0	4
6	1	0
7	1	1
8	1	2
9	1	3
10	1	4

All 5 passes — pass 1 is the card above
pass	`row`
1	0
2	1
3	2
4	3
5	4

25 passes — pass 1 is the card above
pass	`col`
1	0
2	1
3	2
4	3
5	4
6	0
7	1
8	2
9	3
⋯ 14 more passes ⋯
24	3
25	4

All 5 passes — pass 1 is the card above
pass	`row`
1	0
2	1
3	2
4	3
5	4

25 passes — pass 1 is the card above
pass	`col`
1	0
2	1
3	2
4	3
5	4
6	0
7	1
8	2
9	3
⋯ 14 more passes ⋯
24	3
25	4

16 passes — pass 1 is the card above
pass	`row`	`col`
1	0	0
2	0	1
3	0	2
4	0	3
5	0	4
6	1	0
7	1	4
8	2	0
9	2	4
⋯ 5 more passes ⋯
15	4	3
16	4	4

All 5 passes — pass 1 is the card above
pass	`row`
1	0
2	1
3	2
4	3
5	4

Outer loop: rows. Inner loop: columns within each row.

Print triangle pattern

Create a right triangle by varying inner loop iterations.

                            height
                            height = 5 (default)height = 3height = 7
                        

                            triangle.py
                        
Replay: real traced execution (multi-file project)

                            height = 5

# Right triangle (left-aligned)
print("Right triangle:")
for row in range(1, height + 1):
    for col in range(row):
        print("* ", end="")
    print()

# Inverted triangle
print("\nInverted triangle:")
for row in range(height, 0, -1):
    for col in range(row):
        print("* ", end="")
    print()

# Right-aligned triangle
print("\nRight-aligned triangle:")
for row in range(1, height + 1):
    print("  " * (height - row), end="")  # spaces
    print("* " * row)                      # stars

# Pythonic versions
print("\nPythonic right triangle:")
for row in range(1, height + 1):
    print("* " * row)

height = 3

# Right triangle (left-aligned)
print("Right triangle:")
for row in range(1, height + 1):
    for col in range(row):
        print("* ", end="")
    print()

# Inverted triangle
print("\nInverted triangle:")
for row in range(height, 0, -1):
    for col in range(row):
        print("* ", end="")
    print()

# Right-aligned triangle
print("\nRight-aligned triangle:")
for row in range(1, height + 1):
    print("  " * (height - row), end="")  # spaces
    print("* " * row)                      # stars

# Pythonic versions
print("\nPythonic right triangle:")
for row in range(1, height + 1):
    print("* " * row)

height = 7

# Right triangle (left-aligned)
print("Right triangle:")
for row in range(1, height + 1):
    for col in range(row):
        print("* ", end="")
    print()

# Inverted triangle
print("\nInverted triangle:")
for row in range(height, 0, -1):
    for col in range(row):
        print("* ", end="")
    print()

# Right-aligned triangle
print("\nRight-aligned triangle:")
for row in range(1, height + 1):
    print("  " * (height - row), end="")  # spaces
    print("* " * row)                      # stars

# Pythonic versions
print("\nPythonic right triangle:")
for row in range(1, height + 1):
    print("* " * row)


                        
1height ← 51height→ 5 = 5  #@height=3, 723# Right triangle (left-aligned)4print("Right triangle:")5for row in range(1, height + 1):⋯outputRight triangle:
2for row in range(1, height + 1):pass 1 of 5⋯4print("Right triangle:")5for row1 in range(1, height5 + 1):6    for col in range(row):  #?varying_limit7        print("* ", end="")⋯All 5 passes — pass 1 is the card abovepassrow
11
22
33
44
55
3for col in range(row):  #?varying_limitpass 1 of 15⋯5for row in range(1, height + 1):6    for col0 in range(row1):  #?varying_limit7        print("* ", end="")8    print()⋯output* 15 passes — pass 1 is the card abovepasscolrow
101
202
312
403
513
623
704
814
924
⋯ 4 more passes ⋯
1435
1545
4print()⋯7    print("* ", end="")8print()⋯
5print()⋯7    print("* ", end="")8print()⋯
6print()⋯7    print("* ", end="")8print()⋯
7print()⋯7    print("* ", end="")8print()⋯
8print()⋯7    print("* ", end="")8print()⋯
9print(" Inverted triangle:")⋯10# Inverted triangle11print("\nInverted triangle:")12for row in range(height, 0, -1):⋯output
Inverted triangle:
10for row in range(height, 0, -1):pass 1 of 5⋯11print("\nInverted triangle:")12for row5 in range(height5, 0, -1):13    for col in range(row):14        print("* ", end="")⋯All 5 passes — pass 1 is the card abovepassrow
15
24
33
42
51
11for col in range(row):pass 1 of 15⋯12for row in range(height, 0, -1):13    for col0 in range(row5):14        print("* ", end="")15    print()⋯output* 15 passes — pass 1 is the card abovepasscolrow
105
215
325
435
545
604
714
824
934
⋯ 4 more passes ⋯
1412
1501
12print()⋯14    print("* ", end="")15print()⋯
13print()⋯14    print("* ", end="")15print()⋯
14print()⋯14    print("* ", end="")15print()⋯
15print()⋯14    print("* ", end="")15print()⋯
16print()⋯14    print("* ", end="")15print()⋯
17print(" Right-aligned triangle:")⋯17# Right-aligned triangle18print("\nRight-aligned triangle:")19for row in range(1, height + 1):⋯output
Right-aligned triangle:
18for row in range(1, height + 1):pass 1 of 5⋯18print("\nRight-aligned triangle:")19for row1 in range(1, height5 + 1):20    print("  " * (height5 - row1), end="")  # spaces21    print("* " * row1)                      # stars⋯output
* All 5 passes — pass 1 is the card abovepassrow
11
22
33
44
55
19print(" Pythonic right triangle:")⋯23# Pythonic versions24print("\nPythonic right triangle:")25for row in range(1, height + 1):⋯output
Pythonic right triangle:
20for row in range(1, height + 1):pass 1 of 5⋯24print("\nPythonic right triangle:")25for row1 in range(1, height5 + 1):26    print("* " * row1)⋯output* All 5 passes — pass 1 is the card abovepassrow
11
22
33
44
55
1height ← 31height→ 3 = 323# Right triangle (left-aligned)4print("Right triangle:")5for row in range(1, height + 1):⋯outputRight triangle:
2for row in range(1, height + 1):pass 1 of 3⋯4print("Right triangle:")5for row1 in range(1, height3 + 1):6    for col in range(row):7        print("* ", end="")⋯All 3 passes — pass 1 is the card abovepassrow
11
22
33
3for col in range(row):pass 1 of 6⋯5for row in range(1, height + 1):6    for col0 in range(row1):7        print("* ", end="")8    print()⋯output* All 6 passes — pass 1 is the card abovepasscolrow
101
202
312
403
513
623
4print()⋯7    print("* ", end="")8print()⋯
5print()⋯7    print("* ", end="")8print()⋯
6print()⋯7    print("* ", end="")8print()⋯
7print(" Inverted triangle:")⋯10# Inverted triangle11print("\nInverted triangle:")12for row in range(height, 0, -1):⋯output
Inverted triangle:
8for row in range(height, 0, -1):pass 1 of 3⋯11print("\nInverted triangle:")12for row3 in range(height3, 0, -1):13    for col in range(row):14        print("* ", end="")⋯All 3 passes — pass 1 is the card abovepassrow
13
22
31
9for col in range(row):pass 1 of 6⋯12for row in range(height, 0, -1):13    for col0 in range(row3):14        print("* ", end="")15    print()⋯output* All 6 passes — pass 1 is the card abovepasscolrow
103
213
323
402
512
601
10print()⋯14    print("* ", end="")15print()⋯
11print()⋯14    print("* ", end="")15print()⋯
12print()⋯14    print("* ", end="")15print()⋯
13print(" Right-aligned triangle:")⋯17# Right-aligned triangle18print("\nRight-aligned triangle:")19for row in range(1, height + 1):⋯output
Right-aligned triangle:
14for row in range(1, height + 1):pass 1 of 3⋯18print("\nRight-aligned triangle:")19for row1 in range(1, height3 + 1):20    print("  " * (height3 - row1), end="")  # spaces21    print("* " * row1)                      # stars⋯output
* All 3 passes — pass 1 is the card abovepassrow
11
22
33
15print(" Pythonic right triangle:")⋯23# Pythonic versions24print("\nPythonic right triangle:")25for row in range(1, height + 1):⋯output
Pythonic right triangle:
16for row in range(1, height + 1):pass 1 of 3⋯24print("\nPythonic right triangle:")25for row1 in range(1, height3 + 1):26    print("* " * row1)⋯output* All 3 passes — pass 1 is the card abovepassrow
11
22
33
1height ← 71height→ 7 = 723# Right triangle (left-aligned)4print("Right triangle:")5for row in range(1, height + 1):⋯outputRight triangle:
2for row in range(1, height + 1):pass 1 of 7⋯4print("Right triangle:")5for row1 in range(1, height7 + 1):6    for col in range(row):7        print("* ", end="")⋯All 7 passes — pass 1 is the card abovepassrow
11
22
33
44
55
66
77
3for col in range(row):pass 1 of 28⋯5for row in range(1, height + 1):6    for col0 in range(row1):7        print("* ", end="")8    print()⋯output* 28 passes — pass 1 is the card abovepasscolrow
101
202
312
403
513
623
704
814
924
⋯ 17 more passes ⋯
2757
2867
4print()⋯7    print("* ", end="")8print()⋯
5print()⋯7    print("* ", end="")8print()⋯
6print()⋯7    print("* ", end="")8print()⋯
7print()⋯7    print("* ", end="")8print()⋯
8print()⋯7    print("* ", end="")8print()⋯
9print()⋯7    print("* ", end="")8print()⋯
10print()⋯7    print("* ", end="")8print()⋯
11print(" Inverted triangle:")⋯10# Inverted triangle11print("\nInverted triangle:")12for row in range(height, 0, -1):⋯output
Inverted triangle:
12for row in range(height, 0, -1):pass 1 of 7⋯11print("\nInverted triangle:")12for row7 in range(height7, 0, -1):13    for col in range(row):14        print("* ", end="")⋯All 7 passes — pass 1 is the card abovepassrow
17
26
35
44
53
62
71
13for col in range(row):pass 1 of 28⋯12for row in range(height, 0, -1):13    for col0 in range(row7):14        print("* ", end="")15    print()⋯output* 28 passes — pass 1 is the card abovepasscolrow
107
217
327
437
547
657
767
806
916
⋯ 17 more passes ⋯
2712
2801
14print()⋯14    print("* ", end="")15print()⋯
15print()⋯14    print("* ", end="")15print()⋯
16print()⋯14    print("* ", end="")15print()⋯
17print()⋯14    print("* ", end="")15print()⋯
18print()⋯14    print("* ", end="")15print()⋯
19print()⋯14    print("* ", end="")15print()⋯
20print()⋯14    print("* ", end="")15print()⋯
21print(" Right-aligned triangle:")⋯17# Right-aligned triangle18print("\nRight-aligned triangle:")19for row in range(1, height + 1):⋯output
Right-aligned triangle:
22for row in range(1, height + 1):pass 1 of 7⋯18print("\nRight-aligned triangle:")19for row1 in range(1, height7 + 1):20    print("  " * (height7 - row1), end="")  # spaces21    print("* " * row1)                      # stars⋯output
* All 7 passes — pass 1 is the card abovepassrow
11
22
33
44
55
66
77
23print(" Pythonic right triangle:")⋯23# Pythonic versions24print("\nPythonic right triangle:")25for row in range(1, height + 1):⋯output
Pythonic right triangle:
24for row in range(1, height + 1):pass 1 of 7⋯24print("\nPythonic right triangle:")25for row1 in range(1, height7 + 1):26    print("* " * row1)⋯output* All 7 passes — pass 1 is the card abovepassrow
11
22
33
44
55
66
77

All 5 passes — pass 1 is the card above
pass	`row`
1	1
2	2
3	3
4	4
5	5

15 passes — pass 1 is the card above
pass	`col`	`row`
1	0	1
2	0	2
3	1	2
4	0	3
5	1	3
6	2	3
7	0	4
8	1	4
9	2	4
⋯ 4 more passes ⋯
14	3	5
15	4	5

All 5 passes — pass 1 is the card above
pass	`row`
1	5
2	4
3	3
4	2
5	1

15 passes — pass 1 is the card above
pass	`col`	`row`
1	0	5
2	1	5
3	2	5
4	3	5
5	4	5
6	0	4
7	1	4
8	2	4
9	3	4
⋯ 4 more passes ⋯
14	1	2
15	0	1

All 5 passes — pass 1 is the card above
pass	`row`
1	1
2	2
3	3
4	4
5	5

All 5 passes — pass 1 is the card above
pass	`row`
1	1
2	2
3	3
4	4
5	5

All 3 passes — pass 1 is the card above
pass	`row`
1	1
2	2
3	3

All 6 passes — pass 1 is the card above
pass	`col`	`row`
1	0	1
2	0	2
3	1	2
4	0	3
5	1	3
6	2	3

All 3 passes — pass 1 is the card above
pass	`row`
1	3
2	2
3	1

All 6 passes — pass 1 is the card above
pass	`col`	`row`
1	0	3
2	1	3
3	2	3
4	0	2
5	1	2
6	0	1

All 3 passes — pass 1 is the card above
pass	`row`
1	1
2	2
3	3

All 3 passes — pass 1 is the card above
pass	`row`
1	1
2	2
3	3

All 7 passes — pass 1 is the card above
pass	`row`
1	1
2	2
3	3
4	4
5	5
6	6
7	7

28 passes — pass 1 is the card above
pass	`col`	`row`
1	0	1
2	0	2
3	1	2
4	0	3
5	1	3
6	2	3
7	0	4
8	1	4
9	2	4
⋯ 17 more passes ⋯
27	5	7
28	6	7

The inner loop's limit depends on the outer loop variable.

Search in 2D grid

Find a value in a 2D list (matrix).

                            target
                            target = 7 (default)target = 1target = 12target = 99
                        

                            grid_search.py
                        
Replay: real traced execution (multi-file project)

                            grid = [
    [1, 2, 3, 4],
    [5, 6, 7, 8],
    [9, 10, 11, 12]
]
target = 7

# Print the grid
print("Grid:")
for row in grid:
    for cell in row:
        print(f"{cell:3d}", end="")
    print()

# Search for target (using break with flag)
found_pos = None
for row_idx, row in enumerate(grid):
    for col_idx, cell in enumerate(row):
        if cell == target:
            found_pos = (row_idx, col_idx)
            break
    if found_pos:
        break

if found_pos:
    print(f"\nFound {target} at [{found_pos[0]}][{found_pos[1]}]")
else:
    print(f"\n{target} not found in grid")

# Pythonic: using next() with generator
print("\nUsing generator expression:")
result = next(
    ((r, c) for r, row in enumerate(grid) for c, val in enumerate(row) if val == target),
    None
)
print(f"Result: {result}")
grid = [
    [1, 2, 3, 4],
    [5, 6, 7, 8],
    [9, 10, 11, 12]
]
target = 1

# Print the grid
print("Grid:")
for row in grid:
    for cell in row:
        print(f"{cell:3d}", end="")
    print()

# Search for target (using break with flag)
found_pos = None
for row_idx, row in enumerate(grid):
    for col_idx, cell in enumerate(row):
        if cell == target:
            found_pos = (row_idx, col_idx)
            break
    if found_pos:
        break

if found_pos:
    print(f"\nFound {target} at [{found_pos[0]}][{found_pos[1]}]")
else:
    print(f"\n{target} not found in grid")

# Pythonic: using next() with generator
print("\nUsing generator expression:")
result = next(
    ((r, c) for r, row in enumerate(grid) for c, val in enumerate(row) if val == target),
    None
)
print(f"Result: {result}")
grid = [
    [1, 2, 3, 4],
    [5, 6, 7, 8],
    [9, 10, 11, 12]
]
target = 12

# Print the grid
print("Grid:")
for row in grid:
    for cell in row:
        print(f"{cell:3d}", end="")
    print()

# Search for target (using break with flag)
found_pos = None
for row_idx, row in enumerate(grid):
    for col_idx, cell in enumerate(row):
        if cell == target:
            found_pos = (row_idx, col_idx)
            break
    if found_pos:
        break

if found_pos:
    print(f"\nFound {target} at [{found_pos[0]}][{found_pos[1]}]")
else:
    print(f"\n{target} not found in grid")

# Pythonic: using next() with generator
print("\nUsing generator expression:")
result = next(
    ((r, c) for r, row in enumerate(grid) for c, val in enumerate(row) if val == target),
    None
)
print(f"Result: {result}")
grid = [
    [1, 2, 3, 4],
    [5, 6, 7, 8],
    [9, 10, 11, 12]
]
target = 99

# Print the grid
print("Grid:")
for row in grid:
    for cell in row:
        print(f"{cell:3d}", end="")
    print()

# Search for target (using break with flag)
found_pos = None
for row_idx, row in enumerate(grid):
    for col_idx, cell in enumerate(row):
        if cell == target:
            found_pos = (row_idx, col_idx)
            break
    if found_pos:
        break

if found_pos:
    print(f"\nFound {target} at [{found_pos[0]}][{found_pos[1]}]")
else:
    print(f"\n{target} not found in grid")

# Pythonic: using next() with generator
print("\nUsing generator expression:")
result = next(
    ((r, c) for r, row in enumerate(grid) for c, val in enumerate(row) if val == target),
    None
)
print(f"Result: {result}")

                        
1grid ← [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]], target ← 71grid→ [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]] = [2    [1, 2, 3, 4],3    [5, 6, 7, 8],4    [9, 10, 11, 12]5]6target→ 7 = 7  #@target=1, 12, 9978# Print the grid9print("Grid:")10for row in grid:⋯outputGrid:
2for row in grid:pass 1 of 3⋯9print("Grid:")10for row[1, 2, 3, 4] in grid[[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]]:11    for cell in row:12        print(f"{cell:3d}", end="")⋯All 3 passes — pass 1 is the card abovepassrow
1[1, 2, 3, 4]
2[5, 6, 7, 8]
3[9, 10, 11, 12]
3for cell in row:pass 1 of 12⋯10for row in grid:11    for cell1 in row[1, 2, 3, 4]:12        print(f"{cell1:3d}", end="")13    print()⋯output  1All 12 passes — pass 1 is the card abovepasscellrow
11[1, 2, 3, 4]
22[1, 2, 3, 4]
33[1, 2, 3, 4]
44[1, 2, 3, 4]
55[5, 6, 7, 8]
66[5, 6, 7, 8]
77[5, 6, 7, 8]
88[5, 6, 7, 8]
99[9, 10, 11, 12]
1010[9, 10, 11, 12]
1111[9, 10, 11, 12]
1212[9, 10, 11, 12]
4print()⋯12    print(f"{cell:3d}", end="")13print()⋯
5print()⋯12    print(f"{cell:3d}", end="")13print()⋯
6print()⋯12    print(f"{cell:3d}", end="")13print()⋯
7found_pos ← None⋯15# Search for target (using break with flag)16found_pos→ None = None17for row_idx, row in enumerate(grid):⋯
8for row_idx, row in enumerate(grid):pass 1 of 2⋯16found_pos = None17for row_idx0, row[1, 2, 3, 4] in enumerate(grid[[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]]):18    for col_idx, cell in enumerate(row):19        if cell == target:⋯
9for col_idx, cell in enumerate(row):pass 1 of 7⋯17for row_idx, row in enumerate(grid):18    for col_idx0, cell1 in enumerate(row[1, 2, 3, 4]):19        if cell == target:20            found_pos = (row_idx, col_idx)⋯All 7 passes — pass 1 is the card abovepasscol_idxcellrowrow_idxgridtargetfound_pos[0]found_pos[1]found_pos
101[1, 2, 3, 4]——————
212[1, 2, 3, 4]——————
323[1, 2, 3, 4]——————
434[1, 2, 3, 4]1[[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]]————
505[5, 6, 7, 8]——————
616[5, 6, 7, 8]——————
727[5, 6, 7, 8]1—712(1, 2)
10for row_idx, row in enumerate(grid):pass 2 of 2⋯16found_pos = None17for row_idx1, row[5, 6, 7, 8] in enumerate(grid[[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]]):18    for col_idx, cell in enumerate(row):19        if cell == target:⋯
11found_pos ← (1, 2)⋯18for col_idx, cell in enumerate(row):19    if cell7 == target7:20        found_pos→ (1, 2) = (row_idx1, col_idx2)21        break22if found_pos:⋯
12if found_pos:⋯21        break22if found_pos(1, 2):23    break⋯
13if found_pos:⋯25if found_pos(1, 2):26    print(f"\nFound {target7} at [{found_pos[0]1}][{found_pos[1]2}]")27else:⋯output
Found 7 at [1][2]
14result ← (1, 2)⋯30# Pythonic: using next() with generator31print("\nUsing generator expression:")32result→ (1, 2) = next(33    ((r(empty), c(empty)) for r, row[5, 6, 7, 8] in enumerate(grid[[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]]) for c, val(empty) in enumerate(row) if val == target7),34    None35)36print(f"Result: {result(1, 2)}")⋯output
Using generator expression:
Result: (1, 2)
1grid ← [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]], target ← 11grid→ [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]] = [2    [1, 2, 3, 4],3    [5, 6, 7, 8],4    [9, 10, 11, 12]5]6target→ 1 = 178# Print the grid9print("Grid:")10for row in grid:⋯outputGrid:
2for row in grid:pass 1 of 3⋯9print("Grid:")10for row[1, 2, 3, 4] in grid[[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]]:11    for cell in row:12        print(f"{cell:3d}", end="")⋯All 3 passes — pass 1 is the card abovepassrow
1[1, 2, 3, 4]
2[5, 6, 7, 8]
3[9, 10, 11, 12]
3for cell in row:pass 1 of 12⋯10for row in grid:11    for cell1 in row[1, 2, 3, 4]:12        print(f"{cell1:3d}", end="")13    print()⋯output  1All 12 passes — pass 1 is the card abovepasscellrow
11[1, 2, 3, 4]
22[1, 2, 3, 4]
33[1, 2, 3, 4]
44[1, 2, 3, 4]
55[5, 6, 7, 8]
66[5, 6, 7, 8]
77[5, 6, 7, 8]
88[5, 6, 7, 8]
99[9, 10, 11, 12]
1010[9, 10, 11, 12]
1111[9, 10, 11, 12]
1212[9, 10, 11, 12]
4print()⋯12    print(f"{cell:3d}", end="")13print()⋯
5print()⋯12    print(f"{cell:3d}", end="")13print()⋯
6print()⋯12    print(f"{cell:3d}", end="")13print()⋯
7found_pos ← None⋯15# Search for target (using break with flag)16found_pos→ None = None17for row_idx, row in enumerate(grid):⋯
8for row_idx, row in enumerate(grid):⋯16found_pos = None17for row_idx0, row[1, 2, 3, 4] in enumerate(grid[[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]]):18    for col_idx, cell in enumerate(row):19        if cell == target:⋯
9for col_idx, cell in enumerate(row):⋯17for row_idx, row in enumerate(grid):18    for col_idx0, cell1 in enumerate(row[1, 2, 3, 4]):19        if cell == target:20            found_pos = (row_idx, col_idx)⋯
10found_pos ← (0, 0)⋯18for col_idx, cell in enumerate(row):19    if cell1 == target1:20        found_pos→ (0, 0) = (row_idx0, col_idx0)21        break22if found_pos:⋯
11if found_pos:⋯21        break22if found_pos(0, 0):23    break⋯
12if found_pos:⋯25if found_pos(0, 0):26    print(f"\nFound {target1} at [{found_pos[0]0}][{found_pos[1]0}]")27else:⋯output
Found 1 at [0][0]
13result ← (0, 0)⋯30# Pythonic: using next() with generator31print("\nUsing generator expression:")32result→ (0, 0) = next(33    ((r(empty), c(empty)) for r, row[1, 2, 3, 4] in enumerate(grid[[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]]) for c, val(empty) in enumerate(row) if val == target1),34    None35)36print(f"Result: {result(0, 0)}")⋯output
Using generator expression:
Result: (0, 0)
1grid ← [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]], target ← 121grid→ [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]] = [2    [1, 2, 3, 4],3    [5, 6, 7, 8],4    [9, 10, 11, 12]5]6target→ 12 = 1278# Print the grid9print("Grid:")10for row in grid:⋯outputGrid:
2for row in grid:pass 1 of 3⋯9print("Grid:")10for row[1, 2, 3, 4] in grid[[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]]:11    for cell in row:12        print(f"{cell:3d}", end="")⋯All 3 passes — pass 1 is the card abovepassrow
1[1, 2, 3, 4]
2[5, 6, 7, 8]
3[9, 10, 11, 12]
3for cell in row:pass 1 of 12⋯10for row in grid:11    for cell1 in row[1, 2, 3, 4]:12        print(f"{cell1:3d}", end="")13    print()⋯output  1All 12 passes — pass 1 is the card abovepasscellrow
11[1, 2, 3, 4]
22[1, 2, 3, 4]
33[1, 2, 3, 4]
44[1, 2, 3, 4]
55[5, 6, 7, 8]
66[5, 6, 7, 8]
77[5, 6, 7, 8]
88[5, 6, 7, 8]
99[9, 10, 11, 12]
1010[9, 10, 11, 12]
1111[9, 10, 11, 12]
1212[9, 10, 11, 12]
4print()⋯12    print(f"{cell:3d}", end="")13print()⋯
5print()⋯12    print(f"{cell:3d}", end="")13print()⋯
6print()⋯12    print(f"{cell:3d}", end="")13print()⋯
7found_pos ← None⋯15# Search for target (using break with flag)16found_pos→ None = None17for row_idx, row in enumerate(grid):⋯
8for row_idx, row in enumerate(grid):pass 1 of 3⋯16found_pos = None17for row_idx0, row[1, 2, 3, 4] in enumerate(grid[[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]]):18    for col_idx, cell in enumerate(row):19        if cell == target:⋯All 3 passes — pass 1 is the card abovepassrow_idxrowcelltargetcol_idxfound_pos[0]found_pos[1]found_pos
10[1, 2, 3, 4]——————
21[5, 6, 7, 8]——————
32[9, 10, 11, 12]1212323(2, 3)
9for col_idx, cell in enumerate(row):pass 1 of 12⋯17for row_idx, row in enumerate(grid):18    for col_idx0, cell1 in enumerate(row[1, 2, 3, 4]):19        if cell == target:20            found_pos = (row_idx, col_idx)⋯All 12 passes — pass 1 is the card abovepasscol_idxcellrowtargetrow_idxfound_pos[0]found_pos[1]found_pos
101[1, 2, 3, 4]—————
212[1, 2, 3, 4]—————
323[1, 2, 3, 4]—————
434[1, 2, 3, 4]—————
505[5, 6, 7, 8]—————
616[5, 6, 7, 8]—————
727[5, 6, 7, 8]—————
838[5, 6, 7, 8]—————
909[9, 10, 11, 12]—————
10110[9, 10, 11, 12]—————
11211[9, 10, 11, 12]—————
12312[9, 10, 11, 12]12223(2, 3)
10found_pos ← (2, 3)⋯18for col_idx, cell in enumerate(row):19    if cell12 == target12:20        found_pos→ (2, 3) = (row_idx2, col_idx3)21        break22if found_pos:⋯
11if found_pos:⋯21        break22if found_pos(2, 3):23    break⋯
12if found_pos:⋯25if found_pos(2, 3):26    print(f"\nFound {target12} at [{found_pos[0]2}][{found_pos[1]3}]")27else:⋯output
Found 12 at [2][3]
13result ← (2, 3)⋯30# Pythonic: using next() with generator31print("\nUsing generator expression:")32result→ (2, 3) = next(33    ((r(empty), c(empty)) for r, row[9, 10, 11, 12] in enumerate(grid[[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]]) for c, val(empty) in enumerate(row) if val == target12),34    None35)36print(f"Result: {result(2, 3)}")⋯output
Using generator expression:
Result: (2, 3)
1grid ← [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]], target ← 991grid→ [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]] = [2    [1, 2, 3, 4],3    [5, 6, 7, 8],4    [9, 10, 11, 12]5]6target→ 99 = 9978# Print the grid9print("Grid:")10for row in grid:⋯outputGrid:
2for row in grid:pass 1 of 3⋯9print("Grid:")10for row[1, 2, 3, 4] in grid[[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]]:11    for cell in row:12        print(f"{cell:3d}", end="")⋯All 3 passes — pass 1 is the card abovepassrow
1[1, 2, 3, 4]
2[5, 6, 7, 8]
3[9, 10, 11, 12]
3for cell in row:pass 1 of 12⋯10for row in grid:11    for cell1 in row[1, 2, 3, 4]:12        print(f"{cell1:3d}", end="")13    print()⋯output  1All 12 passes — pass 1 is the card abovepasscellrow
11[1, 2, 3, 4]
22[1, 2, 3, 4]
33[1, 2, 3, 4]
44[1, 2, 3, 4]
55[5, 6, 7, 8]
66[5, 6, 7, 8]
77[5, 6, 7, 8]
88[5, 6, 7, 8]
99[9, 10, 11, 12]
1010[9, 10, 11, 12]
1111[9, 10, 11, 12]
1212[9, 10, 11, 12]
4print()⋯12    print(f"{cell:3d}", end="")13print()⋯
5print()⋯12    print(f"{cell:3d}", end="")13print()⋯
6print()⋯12    print(f"{cell:3d}", end="")13print()⋯
7found_pos ← None⋯15# Search for target (using break with flag)16found_pos→ None = None17for row_idx, row in enumerate(grid):⋯
8for row_idx, row in enumerate(grid):pass 1 of 3⋯16found_pos = None17for row_idx0, row[1, 2, 3, 4] in enumerate(grid[[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]]):18    for col_idx, cell in enumerate(row):19        if cell == target:⋯All 3 passes — pass 1 is the card abovepassrow_idxrowtarget
10[1, 2, 3, 4]—
21[5, 6, 7, 8]—
32[9, 10, 11, 12]99
9for col_idx, cell in enumerate(row):pass 1 of 12⋯17for row_idx, row in enumerate(grid):18    for col_idx0, cell1 in enumerate(row[1, 2, 3, 4]):19        if cell == target:20            found_pos = (row_idx, col_idx)⋯All 12 passes — pass 1 is the card abovepasscol_idxcellrowtarget
101[1, 2, 3, 4]—
212[1, 2, 3, 4]—
323[1, 2, 3, 4]—
434[1, 2, 3, 4]—
505[5, 6, 7, 8]—
616[5, 6, 7, 8]—
727[5, 6, 7, 8]—
838[5, 6, 7, 8]—
909[9, 10, 11, 12]—
10110[9, 10, 11, 12]—
11211[9, 10, 11, 12]—
12312[9, 10, 11, 12]99
10else:⋯25if found_pos:26    print(f"\nFound {target} at [{found_pos[0]}][{found_pos[1]}]")27else:28    print(f"\n{target99} not found in grid")⋯output
99 not found in grid
11result ← None⋯30# Pythonic: using next() with generator31print("\nUsing generator expression:")32result→ None = next(33    ((r(empty), c(empty)) for r, row[9, 10, 11, 12] in enumerate(grid[[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]]) for c, val(empty) in enumerate(row) if val == target99),34    None35)36print(f"Result: {resultNone}")⋯output
Using generator expression:
Result: None

Nested loops to traverse all [row][col] positions.

row-major Process row by row: outer loop = rows, inner loop = columns.

Compare all pairs

Find all pairs that satisfy a condition.

                            example
                            numbers = [10, 20, 30, 40], target_sum = 50 (default)numbers = [5, 10, 15, 20, 25]target_sum = 30target_sum = 45
                        

                            pairs.py
                        
Replay: real traced execution (multi-file project)

                            numbers = [10, 20, 30, 40]
target_sum = 50

print(f"Find pairs that sum to {target_sum}:")

# All pairs (avoiding duplicates)
print(f"\nAll pairs with sum {target_sum}:")
for i in range(len(numbers)):
    for j in range(i + 1, len(numbers)):
        if numbers[i] + numbers[j] == target_sum:
            print(f"  {numbers[i]} + {numbers[j]} = {target_sum}")

# All possible pairs (cartesian product)
print("\nAll pairs (order matters):")
for i in range(len(numbers)):
    for j in range(len(numbers)):
        if i != j:
            print(f"  ({numbers[i]}, {numbers[j]})")

# Pythonic: using itertools
from itertools import combinations, permutations

print(f"\nUsing combinations:")
for a, b in combinations(numbers, 2):
    if a + b == target_sum:
        print(f"  {a} + {b} = {target_sum}")

print("\nUsing permutations:")
for pair in permutations(numbers, 2):
    print(f"  {pair}")

numbers = [5, 10, 15, 20, 25]
target_sum = 50

print(f"Find pairs that sum to {target_sum}:")

# All pairs (avoiding duplicates)
print(f"\nAll pairs with sum {target_sum}:")
for i in range(len(numbers)):
    for j in range(i + 1, len(numbers)):
        if numbers[i] + numbers[j] == target_sum:
            print(f"  {numbers[i]} + {numbers[j]} = {target_sum}")

# All possible pairs (cartesian product)
print("\nAll pairs (order matters):")
for i in range(len(numbers)):
    for j in range(len(numbers)):
        if i != j:
            print(f"  ({numbers[i]}, {numbers[j]})")

# Pythonic: using itertools
from itertools import combinations, permutations

print(f"\nUsing combinations:")
for a, b in combinations(numbers, 2):
    if a + b == target_sum:
        print(f"  {a} + {b} = {target_sum}")

print("\nUsing permutations:")
for pair in permutations(numbers, 2):
    print(f"  {pair}")

numbers = [10, 20, 30, 40]
target_sum = 30

print(f"Find pairs that sum to {target_sum}:")

# All pairs (avoiding duplicates)
print(f"\nAll pairs with sum {target_sum}:")
for i in range(len(numbers)):
    for j in range(i + 1, len(numbers)):
        if numbers[i] + numbers[j] == target_sum:
            print(f"  {numbers[i]} + {numbers[j]} = {target_sum}")

# All possible pairs (cartesian product)
print("\nAll pairs (order matters):")
for i in range(len(numbers)):
    for j in range(len(numbers)):
        if i != j:
            print(f"  ({numbers[i]}, {numbers[j]})")

# Pythonic: using itertools
from itertools import combinations, permutations

print(f"\nUsing combinations:")
for a, b in combinations(numbers, 2):
    if a + b == target_sum:
        print(f"  {a} + {b} = {target_sum}")

print("\nUsing permutations:")
for pair in permutations(numbers, 2):
    print(f"  {pair}")

numbers = [10, 20, 30, 40]
target_sum = 45

print(f"Find pairs that sum to {target_sum}:")

# All pairs (avoiding duplicates)
print(f"\nAll pairs with sum {target_sum}:")
for i in range(len(numbers)):
    for j in range(i + 1, len(numbers)):
        if numbers[i] + numbers[j] == target_sum:
            print(f"  {numbers[i]} + {numbers[j]} = {target_sum}")

# All possible pairs (cartesian product)
print("\nAll pairs (order matters):")
for i in range(len(numbers)):
    for j in range(len(numbers)):
        if i != j:
            print(f"  ({numbers[i]}, {numbers[j]})")

# Pythonic: using itertools
from itertools import combinations, permutations

print(f"\nUsing combinations:")
for a, b in combinations(numbers, 2):
    if a + b == target_sum:
        print(f"  {a} + {b} = {target_sum}")

print("\nUsing permutations:")
for pair in permutations(numbers, 2):
    print(f"  {pair}")


                        
1numbers ← [10, 20, 30, 40], target_sum ← 501numbers→ [10, 20, 30, 40] = [10, 20, 30, 40]  #@numbers=[5, 10, 15, 20, 25]2target_sum→ 50 = 50  #@target_sum=30, 4534print(f"Find pairs that sum to {target_sum50}:")56# All pairs (avoiding duplicates)7print(f"\nAll pairs with sum {target_sum50}:")8for i in range(len(numbers)):⋯outputFind pairs that sum to 50:

All pairs with sum 50:
2for i in range(len(numbers)):pass 1 of 4⋯7print(f"\nAll pairs with sum {target_sum}:")8for i0 in range(len(numbers[10, 20, 30, 40])):9    for j in range(i + 1, len(numbers)):  #?avoid_duplicates10        if numbers[i] + numbers[j] == target_sum:⋯All 4 passes — pass 1 is the card abovepassinumbers[i]numbers[j]target_sum
10104050
21203050
32———
43———
3for j in range(i + 1, len(numbers)):  #?avoid_duplicatespass 1 of 6⋯8for i in range(len(numbers)):9    for j1 in range(i0 + 1, len(numbers[10, 20, 30, 40])):  #?avoid_duplicates10        if numbers[i] + numbers[j] == target_sum:11            print(f"  {numbers[i]} + {numbers[j]} = {target_sum}")⋯All 6 passes — pass 1 is the card abovepassjinumbers[i]numbers[j]target_sum
110———
220———
330104050
421203050
531———
632———
4if numbers[i] + numbers[j] == target_sum:pass 1 of 2⋯9for j in range(i + 1, len(numbers)):  #?avoid_duplicates10    if numbers[i]10 + numbers[j]40 == target_sum50:11        print(f"  {numbers[i]10} + {numbers[j]40} = {target_sum50}")⋯output  10 + 40 = 50
5if numbers[i] + numbers[j] == target_sum:pass 2 of 2⋯9for j in range(i + 1, len(numbers)):  #?avoid_duplicates10    if numbers[i]20 + numbers[j]30 == target_sum50:11        print(f"  {numbers[i]20} + {numbers[j]30} = {target_sum50}")⋯output  20 + 30 = 50
6print(" All pairs (order matters):")⋯13# All possible pairs (cartesian product)14print("\nAll pairs (order matters):")15for i in range(len(numbers)):⋯output
All pairs (order matters):
7for i in range(len(numbers)):pass 1 of 4⋯14print("\nAll pairs (order matters):")15for i0 in range(len(numbers[10, 20, 30, 40])):16    for j in range(len(numbers)):17        if i != j:⋯All 4 passes — pass 1 is the card abovepassi
10
21
32
43
8for j in range(len(numbers)):pass 1 of 16⋯15for i in range(len(numbers)):16    for j0 in range(len(numbers[10, 20, 30, 40])):17        if i != j:18            print(f"  ({numbers[i]}, {numbers[j]})")⋯16 passes — pass 1 is the card abovepassj
10
21
32
43
50
61
72
83
90
⋯ 5 more passes ⋯
152
163
9if i != j:pass 1 of 12⋯16for j in range(len(numbers)):17    if i0 != j1:18        print(f"  ({numbers[i]10}, {numbers[j]20})")⋯output  (10, 20)All 12 passes — pass 1 is the card abovepassijnumbers[i]numbers[j]
1011020
2021030
3031040
4102010
5122030
6132040
7203010
8213020
9233040
10304010
11314020
12324030
10print(f" Using combinations:")⋯23print(f"\nUsing combinations:")24for a, b in combinations(numbers, 2):⋯output
Using combinations:
11for a, b in combinations(numbers, 2):pass 1 of 6⋯23print(f"\nUsing combinations:")24for a10, b20 in combinations(numbers[10, 20, 30, 40], 2):25    if a + b == target_sum:26        print(f"  {a} + {b} = {target_sum}")⋯All 6 passes — pass 1 is the card abovepassabtarget_sum
11020—
21030—
3104050
4203050
52040—
63040—
12if a + b == target_sum:pass 1 of 2⋯24for a, b in combinations(numbers, 2):25    if a10 + b40 == target_sum50:26        print(f"  {a10} + {b40} = {target_sum50}")⋯output  10 + 40 = 50
13if a + b == target_sum:pass 2 of 2⋯24for a, b in combinations(numbers, 2):25    if a20 + b30 == target_sum50:26        print(f"  {a20} + {b30} = {target_sum50}")⋯output  20 + 30 = 50
14print(" Using permutations:")⋯28print("\nUsing permutations:")29for pair in permutations(numbers, 2):⋯output
Using permutations:
15for pair in permutations(numbers, 2):pass 1 of 12⋯28print("\nUsing permutations:")29for pair(10, 20) in permutations(numbers[10, 20, 30, 40], 2):30    print(f"  {pair(10, 20)}")⋯output  (10, 20)All 12 passes — pass 1 is the card abovepasspair
1(10, 20)
2(10, 30)
3(10, 40)
4(20, 10)
5(20, 30)
6(20, 40)
7(30, 10)
8(30, 20)
9(30, 40)
10(40, 10)
11(40, 20)
12(40, 30)
1numbers ← [5, 10, 15, 20, 25], target_sum ← 501numbers→ [5, 10, 15, 20, 25] = [5, 10, 15, 20, 25]2target_sum→ 50 = 5034print(f"Find pairs that sum to {target_sum50}:")56# All pairs (avoiding duplicates)7print(f"\nAll pairs with sum {target_sum50}:")8for i in range(len(numbers)):⋯outputFind pairs that sum to 50:

All pairs with sum 50:
2for i in range(len(numbers)):pass 1 of 5⋯7print(f"\nAll pairs with sum {target_sum}:")8for i0 in range(len(numbers[5, 10, 15, 20, 25])):9    for j in range(i + 1, len(numbers)):10        if numbers[i] + numbers[j] == target_sum:⋯All 5 passes — pass 1 is the card abovepassi
10
21
32
43
54
3for j in range(i + 1, len(numbers)):pass 1 of 10⋯8for i in range(len(numbers)):9    for j1 in range(i0 + 1, len(numbers[5, 10, 15, 20, 25])):10        if numbers[i] + numbers[j] == target_sum:11            print(f"  {numbers[i]} + {numbers[j]} = {target_sum}")⋯All 10 passes — pass 1 is the card abovepassji
110
220
330
440
521
631
741
832
942
1043
4print(" All pairs (order matters):")⋯13# All possible pairs (cartesian product)14print("\nAll pairs (order matters):")15for i in range(len(numbers)):⋯output
All pairs (order matters):
5for i in range(len(numbers)):pass 1 of 5⋯14print("\nAll pairs (order matters):")15for i0 in range(len(numbers[5, 10, 15, 20, 25])):16    for j in range(len(numbers)):17        if i != j:⋯All 5 passes — pass 1 is the card abovepassi
10
21
32
43
54
6for j in range(len(numbers)):pass 1 of 25⋯15for i in range(len(numbers)):16    for j0 in range(len(numbers[5, 10, 15, 20, 25])):17        if i != j:18            print(f"  ({numbers[i]}, {numbers[j]})")⋯25 passes — pass 1 is the card abovepassj
10
21
32
43
54
60
71
82
93
⋯ 14 more passes ⋯
243
254
7if i != j:pass 1 of 20⋯16for j in range(len(numbers)):17    if i0 != j1:18        print(f"  ({numbers[i]5}, {numbers[j]10})")⋯output  (5, 10)20 passes — pass 1 is the card abovepassijnumbers[i]numbers[j]
101510
202515
303520
404525
510105
6121015
7131020
8141025
920155
⋯ 9 more passes ⋯
19422515
20432520
8print(f" Using combinations:")⋯23print(f"\nUsing combinations:")24for a, b in combinations(numbers, 2):⋯output
Using combinations:
9for a, b in combinations(numbers, 2):pass 1 of 10⋯23print(f"\nUsing combinations:")24for a5, b10 in combinations(numbers[5, 10, 15, 20, 25], 2):25    if a + b == target_sum:26        print(f"  {a} + {b} = {target_sum}")⋯All 10 passes — pass 1 is the card abovepassab
1510
2515
3520
4525
51015
61020
71025
81520
91525
102025
10print(" Using permutations:")⋯28print("\nUsing permutations:")29for pair in permutations(numbers, 2):⋯output
Using permutations:
11for pair in permutations(numbers, 2):pass 1 of 20⋯28print("\nUsing permutations:")29for pair(5, 10) in permutations(numbers[5, 10, 15, 20, 25], 2):30    print(f"  {pair(5, 10)}")⋯output  (5, 10)20 passes — pass 1 is the card abovepasspair
1(5, 10)
2(5, 15)
3(5, 20)
4(5, 25)
5(10, 5)
6(10, 15)
7(10, 20)
8(10, 25)
9(15, 5)
⋯ 9 more passes ⋯
19(25, 15)
20(25, 20)
1numbers ← [10, 20, 30, 40], target_sum ← 301numbers→ [10, 20, 30, 40] = [10, 20, 30, 40]2target_sum→ 30 = 3034print(f"Find pairs that sum to {target_sum30}:")56# All pairs (avoiding duplicates)7print(f"\nAll pairs with sum {target_sum30}:")8for i in range(len(numbers)):⋯outputFind pairs that sum to 30:

All pairs with sum 30:
2for i in range(len(numbers)):pass 1 of 4⋯7print(f"\nAll pairs with sum {target_sum}:")8for i0 in range(len(numbers[10, 20, 30, 40])):9    for j in range(i + 1, len(numbers)):10        if numbers[i] + numbers[j] == target_sum:⋯All 4 passes — pass 1 is the card abovepassinumbers[i]numbers[j]target_sum
10102030
21———
32———
43———
3for j in range(i + 1, len(numbers)):pass 1 of 6⋯8for i in range(len(numbers)):9    for j1 in range(i0 + 1, len(numbers[10, 20, 30, 40])):10        if numbers[i] + numbers[j] == target_sum:11            print(f"  {numbers[i]} + {numbers[j]} = {target_sum}")⋯All 6 passes — pass 1 is the card abovepassjinumbers[i]numbers[j]target_sum
110102030
220———
330———
421———
531———
632———
4if numbers[i] + numbers[j] == target_sum:⋯9for j in range(i + 1, len(numbers)):10    if numbers[i]10 + numbers[j]20 == target_sum30:11        print(f"  {numbers[i]10} + {numbers[j]20} = {target_sum30}")⋯output  10 + 20 = 30
5print(" All pairs (order matters):")⋯13# All possible pairs (cartesian product)14print("\nAll pairs (order matters):")15for i in range(len(numbers)):⋯output
All pairs (order matters):
6for i in range(len(numbers)):pass 1 of 4⋯14print("\nAll pairs (order matters):")15for i0 in range(len(numbers[10, 20, 30, 40])):16    for j in range(len(numbers)):17        if i != j:⋯All 4 passes — pass 1 is the card abovepassi
10
21
32
43
7for j in range(len(numbers)):pass 1 of 16⋯15for i in range(len(numbers)):16    for j0 in range(len(numbers[10, 20, 30, 40])):17        if i != j:18            print(f"  ({numbers[i]}, {numbers[j]})")⋯16 passes — pass 1 is the card abovepassj
10
21
32
43
50
61
72
83
90
⋯ 5 more passes ⋯
152
163
8if i != j:pass 1 of 12⋯16for j in range(len(numbers)):17    if i0 != j1:18        print(f"  ({numbers[i]10}, {numbers[j]20})")⋯output  (10, 20)All 12 passes — pass 1 is the card abovepassijnumbers[i]numbers[j]
1011020
2021030
3031040
4102010
5122030
6132040
7203010
8213020
9233040
10304010
11314020
12324030
9print(f" Using combinations:")⋯23print(f"\nUsing combinations:")24for a, b in combinations(numbers, 2):⋯output
Using combinations:
10for a, b in combinations(numbers, 2):pass 1 of 6⋯23print(f"\nUsing combinations:")24for a10, b20 in combinations(numbers[10, 20, 30, 40], 2):25    if a + b == target_sum:26        print(f"  {a} + {b} = {target_sum}")⋯All 6 passes — pass 1 is the card abovepassabtarget_sum
1102030
21030—
31040—
42030—
52040—
63040—
11if a + b == target_sum:⋯24for a, b in combinations(numbers, 2):25    if a10 + b20 == target_sum30:26        print(f"  {a10} + {b20} = {target_sum30}")⋯output  10 + 20 = 30
12print(" Using permutations:")⋯28print("\nUsing permutations:")29for pair in permutations(numbers, 2):⋯output
Using permutations:
13for pair in permutations(numbers, 2):pass 1 of 12⋯28print("\nUsing permutations:")29for pair(10, 20) in permutations(numbers[10, 20, 30, 40], 2):30    print(f"  {pair(10, 20)}")⋯output  (10, 20)All 12 passes — pass 1 is the card abovepasspair
1(10, 20)
2(10, 30)
3(10, 40)
4(20, 10)
5(20, 30)
6(20, 40)
7(30, 10)
8(30, 20)
9(30, 40)
10(40, 10)
11(40, 20)
12(40, 30)
1numbers ← [10, 20, 30, 40], target_sum ← 451numbers→ [10, 20, 30, 40] = [10, 20, 30, 40]2target_sum→ 45 = 4534print(f"Find pairs that sum to {target_sum45}:")56# All pairs (avoiding duplicates)7print(f"\nAll pairs with sum {target_sum45}:")8for i in range(len(numbers)):⋯outputFind pairs that sum to 45:

All pairs with sum 45:
2for i in range(len(numbers)):pass 1 of 4⋯7print(f"\nAll pairs with sum {target_sum}:")8for i0 in range(len(numbers[10, 20, 30, 40])):9    for j in range(i + 1, len(numbers)):10        if numbers[i] + numbers[j] == target_sum:⋯All 4 passes — pass 1 is the card abovepassi
10
21
32
43
3for j in range(i + 1, len(numbers)):pass 1 of 6⋯8for i in range(len(numbers)):9    for j1 in range(i0 + 1, len(numbers[10, 20, 30, 40])):10        if numbers[i] + numbers[j] == target_sum:11            print(f"  {numbers[i]} + {numbers[j]} = {target_sum}")⋯All 6 passes — pass 1 is the card abovepassji
110
220
330
421
531
632
4print(" All pairs (order matters):")⋯13# All possible pairs (cartesian product)14print("\nAll pairs (order matters):")15for i in range(len(numbers)):⋯output
All pairs (order matters):
5for i in range(len(numbers)):pass 1 of 4⋯14print("\nAll pairs (order matters):")15for i0 in range(len(numbers[10, 20, 30, 40])):16    for j in range(len(numbers)):17        if i != j:⋯All 4 passes — pass 1 is the card abovepassi
10
21
32
43
6for j in range(len(numbers)):pass 1 of 16⋯15for i in range(len(numbers)):16    for j0 in range(len(numbers[10, 20, 30, 40])):17        if i != j:18            print(f"  ({numbers[i]}, {numbers[j]})")⋯16 passes — pass 1 is the card abovepassj
10
21
32
43
50
61
72
83
90
⋯ 5 more passes ⋯
152
163
7if i != j:pass 1 of 12⋯16for j in range(len(numbers)):17    if i0 != j1:18        print(f"  ({numbers[i]10}, {numbers[j]20})")⋯output  (10, 20)All 12 passes — pass 1 is the card abovepassijnumbers[i]numbers[j]
1011020
2021030
3031040
4102010
5122030
6132040
7203010
8213020
9233040
10304010
11314020
12324030
8print(f" Using combinations:")⋯23print(f"\nUsing combinations:")24for a, b in combinations(numbers, 2):⋯output
Using combinations:
9for a, b in combinations(numbers, 2):pass 1 of 6⋯23print(f"\nUsing combinations:")24for a10, b20 in combinations(numbers[10, 20, 30, 40], 2):25    if a + b == target_sum:26        print(f"  {a} + {b} = {target_sum}")⋯All 6 passes — pass 1 is the card abovepassab
11020
21030
31040
42030
52040
63040
10print(" Using permutations:")⋯28print("\nUsing permutations:")29for pair in permutations(numbers, 2):⋯output
Using permutations:
11for pair in permutations(numbers, 2):pass 1 of 12⋯28print("\nUsing permutations:")29for pair(10, 20) in permutations(numbers[10, 20, 30, 40], 2):30    print(f"  {pair(10, 20)}")⋯output  (10, 20)All 12 passes — pass 1 is the card abovepasspair
1(10, 20)
2(10, 30)
3(10, 40)
4(20, 10)
5(20, 30)
6(20, 40)
7(30, 10)
8(30, 20)
9(30, 40)
10(40, 10)
11(40, 20)
12(40, 30)

Comparing every element with every other element requires O(n²) nested loops.

O(n²) Time complexity when nested loops both iterate n times.

comprehension Python's nested list comprehensions can replace some nested loops.

Exercise: diamond.py

Create a diamond shape pattern with careful loop control

pass	`cell`	`row`
1	1	[1, 2, 3, 4]
2	2	[1, 2, 3, 4]
3	3	[1, 2, 3, 4]
4	4	[1, 2, 3, 4]
5	5	[5, 6, 7, 8]
6	6	[5, 6, 7, 8]
7	7	[5, 6, 7, 8]
8	8	[5, 6, 7, 8]
9	9	[9, 10, 11, 12]
10	10	[9, 10, 11, 12]
11	11	[9, 10, 11, 12]
12	12	[9, 10, 11, 12]

pass	`j`	`i`	`numbers[i]`	`numbers[j]`	`target_sum`
1	1	0	—	—	—
2	2	0	—	—	—
3	3	0	10	40	50
4	2	1	20	30	50
5	3	1	—	—	—
6	3	2	—	—	—

pass	`i`	`j`	`numbers[i]`	`numbers[j]`
1	0	1	10	20
2	0	2	10	30
3	0	3	10	40
4	1	0	20	10
5	1	2	20	30
6	1	3	20	40
7	2	0	30	10
8	2	1	30	20
9	2	3	30	40
10	3	0	40	10
11	3	1	40	20
12	3	2	40	30

pass	`pair`
1	(10, 20)
2	(10, 30)
3	(10, 40)
4	(20, 10)
5	(20, 30)
6	(20, 40)
7	(30, 10)
8	(30, 20)
9	(30, 40)
10	(40, 10)
11	(40, 20)
12	(40, 30)

pass	`i`	`j`	`numbers[i]`	`numbers[j]`
1	0	1	5	10
2	0	2	5	15
3	0	3	5	20
4	0	4	5	25
5	1	0	10	5
6	1	2	10	15
7	1	3	10	20
8	1	4	10	25
9	2	0	15	5
⋯ 9 more passes ⋯
19	4	2	25	15
20	4	3	25	20

pass	`pair`
1	(5, 10)
2	(5, 15)
3	(5, 20)
4	(5, 25)
5	(10, 5)
6	(10, 15)
7	(10, 20)
8	(10, 25)
9	(15, 5)
⋯ 9 more passes ⋯
19	(25, 15)
20	(25, 20)

pass	`j`	`i`	`numbers[i]`	`numbers[j]`	`target_sum`
1	1	0	10	20	30
2	2	0	—	—	—
3	3	0	—	—	—
4	2	1	—	—	—
5	3	1	—	—	—
6	3	2	—	—	—

pass	`i`	`j`	`numbers[i]`	`numbers[j]`
1	0	1	10	20
2	0	2	10	30
3	0	3	10	40
4	1	0	20	10
5	1	2	20	30
6	1	3	20	40
7	2	0	30	10
8	2	1	30	20
9	2	3	30	40
10	3	0	40	10
11	3	1	40	20
12	3	2	40	30

pass	`i`	`j`	`numbers[i]`	`numbers[j]`
1	0	1	10	20
2	0	2	10	30
3	0	3	10	40
4	1	0	20	10
5	1	2	20	30
6	1	3	20	40
7	2	0	30	10
8	2	1	30	20
9	2	3	30	40
10	3	0	40	10
11	3	1	40	20
12	3	2	40	30

pass	`j`	`i`	`numbers[i]`	`numbers[j]`	`target_sum`
1	1	0	—	—	—
2	2	0	—	—	—
3	3	0	10	40	50
4	2	1	20	30	50
5	3	1	—	—	—
6	3	2	—	—	—

pass	`i`	`j`	`numbers[i]`	`numbers[j]`
1	0	1	10	20
2	0	2	10	30
3	0	3	10	40
4	1	0	20	10
5	1	2	20	30
6	1	3	20	40
7	2	0	30	10
8	2	1	30	20
9	2	3	30	40
10	3	0	40	10
11	3	1	40	20
12	3	2	40	30

pass	`j`	`i`	`numbers[i]`	`numbers[j]`	`target_sum`
1	1	0	10	20	30
2	2	0	—	—	—
3	3	0	—	—	—
4	2	1	—	—	—
5	3	1	—	—	—
6	3	2	—	—	—

pass	`i`	`j`	`numbers[i]`	`numbers[j]`
1	0	1	10	20
2	0	2	10	30
3	0	3	10	40
4	1	0	20	10
5	1	2	20	30
6	1	3	20	40
7	2	0	30	10
8	2	1	30	20
9	2	3	30	40
10	3	0	40	10
11	3	1	40	20
12	3	2	40	30

pass	`i`	`j`	`numbers[i]`	`numbers[j]`
1	0	1	10	20
2	0	2	10	30
3	0	3	10	40
4	1	0	20	10
5	1	2	20	30
6	1	3	20	40
7	2	0	30	10
8	2	1	30	20
9	2	3	30	40
10	3	0	40	10
11	3	1	40	20
12	3	2	40	30

pass	`j`	`i`	`numbers[i]`	`numbers[j]`	`target_sum`
1	1	0	—	—	—
2	2	0	—	—	—
3	3	0	10	40	50
4	2	1	20	30	50
5	3	1	—	—	—
6	3	2	—	—	—

pass	`i`	`j`	`numbers[i]`	`numbers[j]`
1	0	1	10	20
2	0	2	10	30
3	0	3	10	40
4	1	0	20	10
5	1	2	20	30
6	1	3	20	40
7	2	0	30	10
8	2	1	30	20
9	2	3	30	40
10	3	0	40	10
11	3	1	40	20
12	3	2	40	30

pass	`j`	`i`	`numbers[i]`	`numbers[j]`	`target_sum`
1	1	0	10	20	30
2	2	0	—	—	—
3	3	0	—	—	—
4	2	1	—	—	—
5	3	1	—	—	—
6	3	2	—	—	—

pass	`i`	`j`	`numbers[i]`	`numbers[j]`
1	0	1	10	20
2	0	2	10	30
3	0	3	10	40
4	1	0	20	10
5	1	2	20	30
6	1	3	20	40
7	2	0	30	10
8	2	1	30	20
9	2	3	30	40
10	3	0	40	10
11	3	1	40	20
12	3	2	40	30

pass	`i`	`j`	`numbers[i]`	`numbers[j]`
1	0	1	10	20
2	0	2	10	30
3	0	3	10	40
4	1	0	20	10
5	1	2	20	30
6	1	3	20	40
7	2	0	30	10
8	2	1	30	20
9	2	3	30	40
10	3	0	40	10
11	3	1	40	20
12	3	2	40	30