How to Handle Exceptions in Python

Exception Handling Basics

Exceptions are errors that occur while a program runs. Python's try/except lets you catch them gracefully instead of crashing.

The try/except Block

try:
    result = 10 / 0
except ZeroDivisionError:
    print("Cannot divide by zero")

Catching Specific Exceptions

try:
    value = int(user_input)
except ValueError:
    print("Not a valid number")
except KeyError:
    print("Missing key")

else and finally

try:
    f = open("data.txt")
except FileNotFoundError:
    print("No file")
else:
    print("File opened OK")   # runs if no exception
finally:
    print("Always runs")      # cleanup, always executes

Raising Your Own

def withdraw(amount):
    if amount < 0:
        raise ValueError("Amount must be positive")

Best Practices

• Catch specific exceptions, not bare except:.
• Use finally or context managers (with) for cleanup.
• Don't silence errors you can't handle.

FAQs

What's wrong with except: pass?

It hides all errors including bugs. Always catch specific types. More in our Python guides.

try/except vs if checks?

Python favors "ask forgiveness" (try/except) for exceptional cases, and if for expected control flow.