Python Errors Explained

21 errors, each with the code that makes it, the exact output and the fix.

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Python NameError: name is not definedNameError: name 'totl' is not defined
Python IndentationError: expected indented blockIndentationError: expected an indented block after 'if' statement on line 2
Python SyntaxError: expected ':'SyntaxError: expected ':'
Python TypeError: can only concatenate strTypeError: can only concatenate str (not "int") to str
Python TypeError: 'NoneType' not subscriptableTypeError: 'NoneType' object is not subscriptable
Python IndexError: list index out of rangeIndexError: list index out of range
Python KeyError: dictionary key not foundKeyError: 'email'
Python ValueError: invalid literal for int()ValueError: invalid literal for int() with base 10: '12.5'
Python AttributeError: object has no attributeAttributeError: 'list' object has no attribute 'push'
Python ModuleNotFoundError: No module namedModuleNotFoundError: No module named 'numpyy'
Python ZeroDivisionError: division by zeroZeroDivisionError: division by zero
Python FileNotFoundError: No such file or directoryFileNotFoundError: [Errno 2] No such file or directory: 'data.txt'
Python UnboundLocalError: local variableUnboundLocalError: cannot access local variable 'count' where it is not associated with a value
Python RecursionError: maximum recursion depthRecursionError: maximum recursion depth exceeded
Python UnicodeDecodeError: utf-8 can't decodeUnicodeDecodeError: 'utf-8' codec can't decode byte 0xe9 in position 3: unexpected end of data
Python TypeError: 'int' object is not iterableTypeError: 'int' object is not iterable
Python TypeError: missing required argumentTypeError: add() missing 1 required positional argument: 'b'
Python TypeError: unhashable type: 'list'TypeError: unhashable type: 'list'
Python JSONDecodeError: Expecting valuejson.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)
Python TypeError: 'str' object is not callableTypeError: 'str' object is not callable
Python ValueError: too many values to unpackValueError: too many values to unpack (expected 2, got 3)

Python error messages are usually clear once you know how to read them: the last line names the type of error and gives a message, and the lines above point to the place in your code. Every page below shows a small program that makes the error, the exact text Python printed when we ran it on 3.14.10, and a corrected version that was run too.

If you are not sure where to start, read how to read a Python traceback first. Then pick the error you see, or paste it into the box on the home page.

This is an independent guide. It is not connected with Python, Microsoft, Google, GitHub or the Git project. Product names belong to their owners. Examples were run on 13 November 2026 in a practice folder or a blank workbook; your version may word a message slightly differently.