How do I get Pyflakes to ignore a statement?

Question

A lot of our modules start with:

try:
    import json
except ImportError:
    from django.utils import simplejson as json  # Python 2.4 fallback.

...and it's the only Pyflakes warning in the entire file:

foo/bar.py:14: redefinition of unused 'json' from line 12

How can I get Pyflakes to ignore this?

(Normally I'd go read the docs but the link is broken. If nobody has an answer, I'll just read the source.)

Answer 1

If you can use flake8 instead - which wraps pyflakes as well as the pep8 checker - a line ending with

# NOQA

(in which the space is significant - 2 spaces between the end of the code and the #, one between it and the NOQA text) will tell the checker to ignore any errors on that line.

Answer 2

I know this was questioned some time ago and is already answered.

But I wanted to add what I usually use:

try:
    import json
    assert json  # silence pyflakes
except ImportError:
    from django.utils import simplejson as json  # Python 2.4 fallback.

Answer 3

Yep, unfortunately dimod.org is down together with all goodies.

Looking at the pyflakes code, it seems to me that pyflakes is designed so that it will be easy to use it as an "embedded fast checker".

For implementing ignore functionality you will need to write your own that calls the pyflakes checker.

Here you can find an idea: http://djangosnippets.org/snippets/1762/

Note that the above snippet only for for comments places on the same line. For ignoring a whole block you might want to add 'pyflakes:ignore' in the block docstring and filter based on node.doc.

Good luck!

---

I am using pocket-lint for all kind of static code analysis. Here are the changes made in pocket-lint for ignoring pyflakes: https://code.launchpad.net/~adiroiban/pocket-lint/907742/+merge/102882

Answer 4

To quote from the github issue ticket:

While the fix is still coming, this is how it can be worked around, if you're wondering:

try:
    from unittest.runner import _WritelnDecorator
    _WritelnDecorator; # workaround for pyflakes issue #13
except ImportError:
    from unittest import _WritelnDecorator

Substitude _unittest and _WritelnDecorator with the entities (modules, functions, classes) you need

-- deemoowoor

Answer 5

Here is a monkey patch for pyflakes that adds a # bypass_pyflakes comment option.

bypass_pyflakes.py

#!/usr/bin/env python

from pyflakes.scripts import pyflakes
from pyflakes.checker import Checker


def report_with_bypass(self, messageClass, *args, **kwargs):
    text_lineno = args[0] - 1
    with open(self.filename, 'r') as code:
        if code.readlines()[text_lineno].find('bypass_pyflakes') >= 0:
            return
    self.messages.append(messageClass(self.filename, *args, **kwargs))

# monkey patch checker to support bypass
Checker.report = report_with_bypass

pyflakes.main()

If you save this as bypass_pyflakes.py, then you can invoke it as python bypass_pyflakes.py myfile.py.

http://chase-seibert.github.com/blog/2013/01/11/bypass_pyflakes.html

Answer 6

Flake gives you some options to ignore violations.

My favorite one is to make it explicit and ignore the specific violation inline:

my invalid code # noqa: WS03

And you have the others already cited options.

1. Ignore all validations in the line:

my invalid code # NOQA

2. Ignore all validations in the file. Put in its first line:

# flake8: noqa: E121, E131, E241, F403, F405

Or configure to ignore it as a parameter in you flake8 configuration.

Answer 7

You can also import with __import__. It's not pythonic, but pyflakes does not warn you anymore. See documentation for __import__ .

try:
    import json
except ImportError:
    __import__('django.utils', globals(), locals(), ['json'], -1)

Answer 8

I created a little shell script with some awk magic to help me. With this all lines with import typing, from typing import or #$ (latter is a special comment I am using here) are excluded ($1 is the file name of the Python script):

result=$(pyflakes -- "$1" 2>&1)

# check whether there is any output
if [ "$result" ]; then

    # lines to exclude
    excl=$(awk 'BEGIN { ORS="" } /(#\$)|(import +typing)|(from +typing +import )/ { print sep NR; sep="|" }' "$1")

    # exclude lines if there are any (otherwise we get invalid regex)
    [ "$excl" ] &&
        result=$(awk "! /^[^:]+:(${excl}):/" <<< "$result")

fi

# now echo "$result" or such ...

Basically it notes the line numbers and dynamically creates a regex out it.

Answer 9

For flake8, which is recommended alternative (compare flake8 vs pyflakes here)

Add the first line like:

# flake8: noqa: E121, E131, E241, F403, F405

in general:

# flake8: noqa: <code>[, <code> ...]

This way in one line you can silent the entire file and do it for many ignore statements at once, which is often a case.