Python Cheat Sheet: Errors and Exception Handling

1. Basic Exception Handling

try:
    result = 10 / 0
except ZeroDivisionError:
    print("You can't divide by zero!")

2. Catching Multiple Exceptions

try:
    # some code
    pass
except (TypeError, ValueError) as e:
    print("Caught:", e)

3. Using else and finally

try:
    x = 5 / 1
except ZeroDivisionError:
    print("Error!")
else:
    print("No error occurred")
finally:
    print("Always runs")

4. Catching All Exceptions (use with caution)

try:
    risky_operation()
except Exception as e:
    print("Caught error:", e)

5. Raising Exceptions

def divide(a, b):
    if b == 0:
        raise ValueError("Cannot divide by zero")
    return a / b

6. Custom Exceptions

class MyCustomError(Exception):
    pass

raise MyCustomError("Something went wrong")

7. Common Built-in Exceptions

• ZeroDivisionError
• TypeError
• ValueError
• IndexError
• KeyError
• FileNotFoundError
• AttributeError
• ImportError

8. Suppressing Exceptions with contextlib

from contextlib import suppress

with suppress(FileNotFoundError):
    open("nonexistent.txt")

9. Assertions

x = 10
assert x > 0, "x must be positive"  # Raises AssertionError if condition is False