Python Error Fixes 🐍🔧

A searchable index of the Python errors beginners hit most — what they mean, why they happen, and how to fix them.

Paste your error message into your editor's search (or use Ctrl/Cmd+F on this page) and jump to the fix. Each entry links to a full, step-by-step walkthrough on pythonbeginner.help.

How to read a Python traceback

Python prints the last line of a traceback as the error type and message — read it bottom-up:

Traceback (most recent call last):
  File "app.py", line 3, in <module>
    print(items[5])
          ~~~~~^^^
IndexError: list index out of range

The error type (IndexError) tells you the category; the message (list index out of range) tells you the specifics. Find your type below.

Error index

Error	Typical message	Common cause	Fix
AttributeError	'NoneType' object has no attribute 'x'	Using the result of a function that returned None	Fix →
AttributeError	'list' object has no attribute 'x'	Calling a string/dict method on a list	Fix →
AttributeError	'str' object has no attribute 'x'	Treating a string like a list or number	Fix →
IndexError	list index out of range	Index ≥ length of the list	Fix →
IndexError	tuple index out of range	Index past the end of a tuple	Fix →
KeyError	'somekey'	Reading a dict key that doesn't exist	Fix →
IndentationError	unexpected indent	A line is indented when it shouldn't be	Fix →
IndentationError	expected an indented block	A block (after :) is empty or not indented	Fix →
ImportError	No module named 'x'	Package not installed or wrong name	Fix →
ImportError	cannot import name 'x'	Name doesn't exist / circular import	Fix →
FileNotFoundError	[Errno 2] No such file or directory	Wrong path or working directory	Fix →
AssertionError	(often blank)	An assert condition was False	Fix →

Quick fixes by example

IndexError: list index out of range

items = ["a", "b", "c"]
print(items[3])   # ✗ valid indexes are 0, 1, 2

items = ["a", "b", "c"]
if len(items) > 3:
    print(items[3])   # ✓ check the length first

Full explanation →

KeyError: 'name'

user = {"id": 1}
print(user["name"])        # ✗ key 'name' is missing

user = {"id": 1}
print(user.get("name"))    # ✓ returns None instead of crashing
print(user.get("name", "Anonymous"))  # ✓ with a default

Full explanation →

AttributeError: 'NoneType' object has no attribute ...

result = my_list.sort()   # sort() returns None, not the list
result.append(5)          # ✗ result is None

my_list.sort()            # ✓ sorts in place
my_list.append(5)         # ✓ use the list itself

Full explanation →

More

• 📚 Full error library: pythonbeginner.help/errors
• 🧠 New to tracebacks? Start with the common errors beginner guide.
• 🏋️ Practice: python-beginner-exercises

License

Released under CC0 1.0 by pythonbeginner.help — use it however you like.