Warning / Error codes

The convention of Flake8 is to assign a code to each error or warning, like the pep8 tool. These codes are used to configure the list of errors which are selected or ignored.

Each code consists of an upper case ASCII letter followed by three digits. The recommendation is to use a different prefix for each plugin. A list of the known prefixes is published below:

• E***/W***: pep8 errors and warnings
• F***: PyFlakes codes (see below)
• C9**: McCabe complexity plugin mccabe
• N8**: Naming Conventions plugin pep8-naming

The original PyFlakes does not provide error codes. Flake8 patches the PyFlakes messages to add the following codes:

code	sample message
F401	module imported but unused
F402	import module from line N shadowed by loop variable
F403	‘from module import *’ used; unable to detect undefined names
F404	future import(s) name after other statements
F811	redefinition of unused name from line N
F812	list comprehension redefines name from line N
F821	undefined name name
F822	undefined name name in __all__
F823	local variable name ... referenced before assignment
F831	duplicate argument name in function definition
F841	local variable name is assigned to but never used