NameError

NameError is raised when Python encounters a name (variable, function, class) that hasn't been defined in the current scope. This includes typos, variables used before assignment, and missing imports.

Common causes

• Using a variable before assigning it
• Typo in variable or function name
• Forgetting to import a module or name
• Variable defined inside a function but used outside
• Using a Python 2 name in Python 3 (e.g., print without parentheses, raw_input)

How to fix it

• Define variables before using them
• Check for typos in names
• Add import statements for external modules
• Check variable scope — local vs global
• Use globals() or locals() to inspect available names

Example

# Error example
print(user_name)
# NameError: name 'user_name' is not defined

pritn("hello")
# NameError: name 'pritn' is not defined

# Fix: define before use
user_name = "Alice"
print(user_name)  # "Alice"

# Fix: correct the typo
print("hello")

# Fix: add missing import
from datetime import datetime
now = datetime.now()

Related errors