TypeError: object of type 'NoneType' has no len()
TypeError: object of type 'NoneType' has no len() in Python means you called len() on a value that is None. Usually a function forgot to return its result, or a lookup returned None when nothing was found.
How do I fix TypeError: object of type 'NoneType' has no len()?
To fix TypeError: object of type 'NoneType' has no len() in Python, locate the line causing the error and check the values right before it runs. Most occurrences happen because of a function has no return statement. Apply a defensive check or safe fallback, make sure collections or objects exist before access, and verify return values from upstream functions.
What does TypeError: object of type 'NoneType' has no len() mean?
len() requires a sequence or container (such as a string, list, dictionary, or tuple). None represents the absence of a value and does not define a length. This error means your code assumed a valid list or string was present, but got None instead.
Why does TypeError: object of type 'NoneType' has no len() happen?
1. A function has no return statement
Functions without an explicit return statement implicitly return None.
Breaks
def get_items():
items = [1, 2, 3]
count = len(get_items())Works
def get_items():
items = [1, 2, 3]
return items
count = len(get_items())2. Calling len() on a mutating method's return value
list.sort(), list.append(), and list.reverse() modify the list in place and return None.
Breaks
count = len(items.sort())Works
items.sort()
count = len(items)3. dict.get() or regex match returned None
When a key is missing or pattern does not match, the result is None.
Breaks
tags = user.get("tags")
num_tags = len(tags)Works
tags = user.get("tags", [])
num_tags = len(tags)How to find it in your own code
Provide a fallback value (e.g. `user.get("tags", [])` or `val = result or ""`) before calling len(), or check `if value is not None:` first.
Try it: fix this bug
easyshipping_cost(20) returns None. Big orders correctly get 0.
def shipping_cost(total):
if total >= 50:
return 0
else:
shipping = 5More challenges with this error
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