NameError: name 'x' is not defined

What it does

Checks for references to names that are possibly not defined.

Why is this bad?

Using an undefined variable will raise a NameError at runtime.

Rule status

This rule is currently disabled by default because of the number of false positives it can produce.

Example

for i in range(0):
    x = i

# NameError: name 'x' is not defined
print(x)  # error