Bugs
Python NoneType Errors: Causes and Fixes
The AttributeError: NoneType object has no attribute error is one of the most frequent Python runtime crashes. It occurs when you call a method on a variable that holds None.
❌ Buggy Code
def get_user(user_id):
return db.query('SELECT * FROM users WHERE id = ?', (user_id,)).fetchone()
user = get_user(42)
print(user.name) # Crashes if user is None✅ Fixed with Null Guard
def get_user(user_id):
return db.query('SELECT * FROM users WHERE id = ?', (user_id,)).fetchone()
user = get_user(42)
if user is None:
print('User not found')
else:
print(user.name)💡
Pro tip: Always check for None before accessing attributes on values that may not exist. Use Optional type hints to make nullability explicit.
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