Why do I get AttributeError: 'NoneType' object has no attribute 'something'?

python

attributeerror

error-handling

best-practices

byAnton Shumikhin·Mar 13, 2025

The error AttributeError: 'NoneType' object has no attribute 'something' occurs when an attribute or method is invoked on None. This signals that the variable you're using isn't assigned a valid object. Ensure the object isn't None prior to attribute access:

if my_variable:
    result = my_variable.something()
else:
    print("my_variable is having an existential crisis!")

Quick fix example:

# Failsafe attribute access
result = my_variable.something() if my_variable else None

Inspect that functions return non-None objects as expected, or modify your code to handle None cases to avoid the error.

Tracing down the None invasion

Whenever AttributeError strikes, always trace back to where the variable was originally set. It could be due to a failed assignment or a function that promised to return an object but instead gave you None.

Don't take your functions for granted

Guarantee that your functions are emphatically clear about their return intentions. Remember: If a function loses its return statement, it strides down the None alleyway. Better be safe: consider returning a boolean status or an indicative value even when it's not essentially needed. The more information in debugging, the better.

Avengers Assemble! The `getattr` as your failsafe maneuver

When facing Thanos with his mighty AttributeError, call upon getattr. This function charmingly dismisses AttributeError, replacing it with a default value if the attribute doesn't exist:

# getattr to the rescue!
attribute = getattr(my_variable, 'something', None)

Avengers' strategy: Plan ahead with conditionals and assertions

Implement strategic checks for None in your code, create a safety net where a variable is expected to be an instance of a certain class. You might find Python's assert statement - Captain America of debugging. Always keeps your hands clean.

# Assert that a variable is having a body and soul
assert my_variable is not None, "my_variable is currently a ghost. Happy Halloween!"

Best practices to prevent AttributeError

Timely object initializations

Ensure appropriate initialization of your objects. Whether you set default values in your class's __init__ method, or validate object creation functions' output, taking the reins of object initialization avoids abrupt halts.

Error-Handling: Always on the guard

Make use of try-except blocks to catch AttributeErrors: they provide an escape route as well as a friendly error message.

try:
    value = my_variable.something()
except AttributeError:
    value = "default_value"
    print("my_variable decided to be a rebel! Using a decoy...")

In scenarios where None is a potentially reasonable and acceptable value, this is particularly useful.

Going beyond: type annotations

Python supports type hints that help in notifying where the elements don't align. Remember, they don't affect runtime behavior but provide insightful guidance.

def process_data(data: MyObject) -> None:
    # Process data assuming 'data' is of type 'MyObject'
    ...

# Static type checkers like mypy can show warnings if 'None' is passed