NameError: name 'x' is not defined — how to fix

Traceback (most recent call last):
  File "main.py", line 3, in <module>
    print(total)
NameError: name 'total' is not defined

Quick fix: Check spelling and case, add the missing import (import os, from datetime import datetime), make sure the variable is assigned before the line that uses it (and on every branch), and in notebooks re-run the cell that defines it. Quote strings: input('yes') not input(yes).

What it means

When Python executes a name, it searches local scope, then enclosing functions, then module globals, then builtins (the LEGB rule). If the name isn't found anywhere, you get NameError. Python 3.10+ often adds a hint like Did you mean: 'totals'? or Did you forget to import 'os'?.

Cause 1: typo or wrong case

Names are case-sensitive: Total, total and totla are different.

count = 5
print(Count)    # NameError: name 'Count' is not defined. Did you mean: 'count'?

Also common: true/false/null from other languages. Python uses True, False, None.

Cause 2: missing import

print(os.getcwd())        # NameError: name 'os' is not defined

import os
from datetime import datetime
import numpy as np        # then use np, not numpy
import pandas as pd

If you wrote from math import sqrt, then math.pi is undefined; only sqrt was imported.

Cause 3: used before it's assigned

Code runs top to bottom. A function or variable defined later in the file doesn't exist yet:

greet()          # NameError
def greet():
    print("hi")

Move the definition above the call, or put the calling code in a main() called at the bottom:

def main():
    greet()

def greet():
    print("hi")

if __name__ == "__main__":
    main()

Cause 4: assigned only on some branches

if score > 50:
    result = "pass"
print(result)     # NameError if score <= 50 (at module level)

Initialise before the branch: result = None (or "fail"). Inside a function the same bug raises UnboundLocalError, a subclass of NameError.

Same with try:

try:
    data = load()
except IOError:
    pass
print(data)       # NameError if load() failed

Cause 5: scope - the name lives in another function

Variables created inside a function are local to it:

def setup():
    config = {"debug": True}

setup()
print(config)     # NameError

Return the value instead: config = setup() with return config in the function.

List comprehension variables and except ... as e names also don't exist after the block (e is deleted when the except block ends).

Cause 6: a string without quotes

name = input(Enter your name)      # SyntaxError
choice = input("y/n: ")
if choice == yes:                  # NameError: name 'yes' is not defined

Should be choice == "yes". In Python 2, input() evaluated what was typed, so typing a word caused this error; run the script with python3.

Cause 7: Jupyter / interactive sessions

Notebook cells share state only if they've been run. After a kernel restart, every name is gone. Use "Run All" or re-run the cell that defines the variable/import. Running cells out of order is the usual reason code "works on my machine" but fails on a fresh run.

Cause 8: class attributes and self

Inside a method, instance and class attributes must be accessed through self (or the class name):

class Cart:
    tax = 0.2
    def total(self, price):
        return price * (1 + tax)       # NameError
        # fix: return price * (1 + self.tax)

Last updated 2026-11-01.