Common Python Errors & How to Fix Them

# 1. SyntaxError — invalid Python syntax
# if x == 5  # missing colon!
# print "hello"  # Python 3 needs parentheses

# 2. NameError — using undefined variable
try:
    print(undefined_var)
except NameError as e:
    print(f"NameError: {e}")

# 3. TypeError — wrong type for operation
try:
    result = "5" + 3
except TypeError as e:
    print(f"TypeError: {e}")
    print("Fix: result = int('5') + 3")

# 4. IndexError — index out of range
try:
    items = [1, 2, 3]
    print(items[10])
except IndexError as e:
    print(f"IndexError: {e}")
    print("Fix: check len(items) first")

# 5. KeyError — missing dictionary key
try:
    data = {"name": "Alice"}
    print(data["age"])
except KeyError as e:
    print(f"KeyError: {e}")
    print("Fix: use data.get('age', 'default')")

# 6. AttributeError — missing attribute/method
try:
    x = 42
    x.append(5)
except AttributeError as e:
    print(f"AttributeError: {e}")
    print("Fix: x is int, not a list")

# 7. ValueError — right type, wrong value
try:
    num = int("hello")
except ValueError as e:
    print(f"ValueError: {e}")

# 8. IndentationError
print("\nIndentation: always use 4 spaces!")

# Debugging checklist:
print("\n=== Debugging Checklist ===")
tips = ["Read the error message carefully", "Check the line number",
        "print() variables before the error", "Check types with type()",
        "Google the error message", "Use breakpoint() to step through"]
for i, tip in enumerate(tips, 1):
    print(f"  {i}. {tip}")