Error Collection

Collecting all validation errors lets a caller see every problem in one pass.

errors.py

def validate_order(quantity, price):
    errors = []

    if quantity <= 0:
        errors.append("quantity")
    if price <= 0:
        errors.append("price")

    return errors


price = 
errors = validate_order(2, price)

print("errors=" + ",".join(errors) if errors else "errors=none")

def validate_order(quantity, price):
    errors = []

    if quantity <= 0:
        errors.append("quantity")
    if price <= 0:
        errors.append("price")

    return errors


price = 
errors = validate_order(2, price)

print("errors=" + ",".join(errors) if errors else "errors=none")

error collection Instead of stopping at the first invalid field, collect each error message into a list.