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|
.. _error_codes:
=========================
Error / Violation Codes
=========================
Flake8 and its plugins assign a code to each message that we refer to as an
:term:`error code` (or :term:`violation`). Most plugins will list their error
codes in their documentation or README.
Flake8 installs ``pycodestyle``, ``pyflakes``, and ``mccabe`` by default and
generates its own :term:`error code`\ s for ``pyflakes``:
+------+---------------------------------------------------------------------+
| Code | Example 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 |
+------+---------------------------------------------------------------------+
| F405 | ``name`` may be undefined, or defined from star imports: ``module`` |
+------+---------------------------------------------------------------------+
| F406 | 'from ``module`` import \*' only allowed at module level |
+------+---------------------------------------------------------------------+
| F407 | an undefined ``__future__`` feature name was imported |
+------+---------------------------------------------------------------------+
+------+---------------------------------------------------------------------+
| F501 | invalid ``%`` format literal |
+------+---------------------------------------------------------------------+
| F502 | ``%`` format expected mapping but got sequence |
+------+---------------------------------------------------------------------+
| F503 | ``%`` format expected sequence but got mapping |
+------+---------------------------------------------------------------------+
| F504 | ``%`` format unused named arguments |
+------+---------------------------------------------------------------------+
| F505 | ``%`` format missing named arguments |
+------+---------------------------------------------------------------------+
| F506 | ``%`` format mixed positional and named arguments |
+------+---------------------------------------------------------------------+
| F507 | ``%`` format mismatch of placeholder and argument count |
+------+---------------------------------------------------------------------+
| F508 | ``%`` format with ``*`` specifier requires a sequence |
+------+---------------------------------------------------------------------+
| F509 | ``%`` format with unsupported format character |
+------+---------------------------------------------------------------------+
| F521 | ``.format(...)`` invalid format string |
+------+---------------------------------------------------------------------+
| F522 | ``.format(...)`` unused named arguments |
+------+---------------------------------------------------------------------+
| F523 | ``.format(...)`` unused positional arguments |
+------+---------------------------------------------------------------------+
| F524 | ``.format(...)`` missing argument |
+------+---------------------------------------------------------------------+
| F525 | ``.format(...)`` mixing automatic and manual numbering |
+------+---------------------------------------------------------------------+
| F541 | f-string without any placeholders |
+------+---------------------------------------------------------------------+
+------+---------------------------------------------------------------------+
| F601 | dictionary key ``name`` repeated with different values |
+------+---------------------------------------------------------------------+
| F602 | dictionary key variable ``name`` repeated with different values |
+------+---------------------------------------------------------------------+
| F621 | too many expressions in an assignment with star-unpacking |
+------+---------------------------------------------------------------------+
| F622 | two or more starred expressions in an assignment ``(a, *b, *c = d)``|
+------+---------------------------------------------------------------------+
| F631 | assertion test is a tuple, which is always ``True`` |
+------+---------------------------------------------------------------------+
| F632 | use ``==/!=`` to compare ``str``, ``bytes``, and ``int`` literals |
+------+---------------------------------------------------------------------+
| F633 | use of ``>>`` is invalid with ``print`` function |
+------+---------------------------------------------------------------------+
| F634 | if test is a tuple, which is always ``True`` |
+------+---------------------------------------------------------------------+
+------+---------------------------------------------------------------------+
| F701 | a ``break`` statement outside of a ``while`` or ``for`` loop |
+------+---------------------------------------------------------------------+
| F702 | a ``continue`` statement outside of a ``while`` or ``for`` loop |
+------+---------------------------------------------------------------------+
| F704 | a ``yield`` or ``yield from`` statement outside of a function |
+------+---------------------------------------------------------------------+
| F706 | a ``return`` statement outside of a function/method |
+------+---------------------------------------------------------------------+
| F707 | an ``except:`` block as not the last exception handler |
+------+---------------------------------------------------------------------+
| F721 | syntax error in doctest |
+------+---------------------------------------------------------------------+
| F722 | syntax error in forward annotation |
+------+---------------------------------------------------------------------+
| F723 | syntax error in type comment |
+------+---------------------------------------------------------------------+
+------+---------------------------------------------------------------------+
| F811 | redefinition of unused ``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 |
+------+---------------------------------------------------------------------+
+------+---------------------------------------------------------------------+
| F901 | ``raise NotImplemented`` should be ``raise NotImplementedError`` |
+------+---------------------------------------------------------------------+
We also report one extra error: ``E999``. We report ``E999`` when we fail to
compile a file into an Abstract Syntax Tree for the plugins that require it.
``mccabe`` only ever reports one :term:`violation` - ``C901`` based on the
complexity value provided by the user.
Users should also reference `pycodestyle's list of error codes`_.
.. links
.. _pycodestyle's list of error codes:
https://pycodestyle.readthedocs.io/en/latest/intro.html#error-codes
|
