Check for python builtins being used as variables or parameters

Gil Forcada Codinachs

Last update: Jan 8, 2023

Overview

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Flake8 Builtins plugin

Check for python builtins being used as variables or parameters.

Imagine some code like this:

def max_values(list, list2):
    max = list[0]
    for x in list:
        if x > 0:
            max = x

    all_values = list()
    all_values.append(max)

    max = list2[0]
    for x in list2:
        if x > 0:
            max = x
    all_values.append(max)

    return all_values

max_values([3, 4, 5, ], [5, 6, 7])

The last statement is not returning [5, 7] as one would expect, instead is raising this exception:

Traceback (most recent call last):
  File "test.py", line 17, in <module>
    max_values([3,4,5], [4,5,6])
  File "bla.py", line 6, in max_values
    all_values = list()
TypeError: 'list' object is not callable

Why? Because max_value function's first argument is list a Python builtin. Python allows to override them, but although could be useful in some really specific use cases, the general approach is to not do that as code then can suddenly break without a clear trace.

Example

Given the following code:

def my_method(object, list, dict):
    max = 5
    min = 3
    zip = (4, 3)

The following warnings are shown (via flake8):

test.py:1:15: A002 argument "object" is shadowing a python builtin
test.py:1:23: A002 argument "list" is shadowing a python builtin
test.py:1:29: A002 argument "dict" is shadowing a python builtin
test.py:2:5: A001 variable "max" is shadowing a python builtin
test.py:3:5: A001 variable "min" is shadowing a python builtin
test.py:4:5: A001 variable "zip" is shadowing a python builtin

Install

Install with pip:

$ pip install flake8-builtins

Requirements

Python 2.7, 3.6, 3.7, 3.8
flake8

License

GPL 2.0

Comments

Split A002 to differentiate between arguments and class-level variables
E.g. with the latest version (1.2.1) I have a few examples of things like this:

class MyClass(object): def filter(self, a, b): pass

This now fails with a message:

A002 "filter" is used as an argument and thus shadows a python builtin, consider renaming the argument

This text doesn't really make sense (filter isn't an argument).
opened by clokep 12

Traceback from flake8-bugbear

Similar to #35 I see some weird interaction with flake8-bugbear since upgrading flake8-builtins to 1.4.0. Here's what I get:

multiprocessing.pool.RemoteTraceback: 
"""
Traceback (most recent call last):
  File "/opt/python/3.6.3/lib/python3.6/multiprocessing/pool.py", line 119, in worker
    result = (True, func(*args, **kwds))
  File "/opt/python/3.6.3/lib/python3.6/multiprocessing/pool.py", line 44, in mapstar
    return list(map(*args))
  File "/home/travis/build/qutebrowser/qutebrowser/.tox/flake8/lib/python3.6/site-packages/flake8/checker.py", line 648, in _run_checks
    return checker.run_checks()
  File "/home/travis/build/qutebrowser/qutebrowser/.tox/flake8/lib/python3.6/site-packages/flake8/checker.py", line 579, in run_checks
    self.run_ast_checks()
  File "/home/travis/build/qutebrowser/qutebrowser/.tox/flake8/lib/python3.6/site-packages/flake8/checker.py", line 493, in run_ast_checks
    for (line_number, offset, text, check) in runner:
  File "/home/travis/build/qutebrowser/qutebrowser/.tox/flake8/lib/python3.6/site-packages/bugbear.py", line 37, in run
    visitor.visit(self.tree)
  File "/home/travis/build/qutebrowser/qutebrowser/.tox/flake8/lib/python3.6/site-packages/bugbear.py", line 143, in visit
    super().visit(node)
  File "/opt/python/3.6.3/lib/python3.6/ast.py", line 253, in visit
    return visitor(node)
  File "/opt/python/3.6.3/lib/python3.6/ast.py", line 261, in generic_visit
    self.visit(item)
  File "/home/travis/build/qutebrowser/qutebrowser/.tox/flake8/lib/python3.6/site-packages/bugbear.py", line 143, in visit
    super().visit(node)
  File "/opt/python/3.6.3/lib/python3.6/ast.py", line 253, in visit
    return visitor(node)
  File "/home/travis/build/qutebrowser/qutebrowser/.tox/flake8/lib/python3.6/site-packages/bugbear.py", line 235, in visit_ClassDef
    self.check_for_b903(node)
  File "/home/travis/build/qutebrowser/qutebrowser/.tox/flake8/lib/python3.6/site-packages/bugbear.py", line 414, in check_for_b903
    if len(targets) > 1 or not isinstance(targets[0], ast.Attribute):
IndexError: list index out of range
"""
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
  File "/opt/python/3.6.3/lib/python3.6/runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "/opt/python/3.6.3/lib/python3.6/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/home/travis/build/qutebrowser/qutebrowser/.tox/flake8/lib/python3.6/site-packages/flake8/__main__.py", line 4, in <module>
    cli.main()
  File "/home/travis/build/qutebrowser/qutebrowser/.tox/flake8/lib/python3.6/site-packages/flake8/main/cli.py", line 16, in main
    app.run(argv)
  File "/home/travis/build/qutebrowser/qutebrowser/.tox/flake8/lib/python3.6/site-packages/flake8/main/application.py", line 396, in run
    self._run(argv)
  File "/home/travis/build/qutebrowser/qutebrowser/.tox/flake8/lib/python3.6/site-packages/flake8/main/application.py", line 384, in _run
    self.run_checks()
  File "/home/travis/build/qutebrowser/qutebrowser/.tox/flake8/lib/python3.6/site-packages/flake8/main/application.py", line 310, in run_checks
    self.file_checker_manager.run()
  File "/home/travis/build/qutebrowser/qutebrowser/.tox/flake8/lib/python3.6/site-packages/flake8_per_file_ignores.py", line 33, in run
    orig_run(self)
  File "/home/travis/build/qutebrowser/qutebrowser/.tox/flake8/lib/python3.6/site-packages/flake8/checker.py", line 319, in run
    self.run_parallel()
  File "/home/travis/build/qutebrowser/qutebrowser/.tox/flake8/lib/python3.6/site-packages/flake8/checker.py", line 288, in run_parallel
    for ret in pool_map:
  File "/opt/python/3.6.3/lib/python3.6/multiprocessing/pool.py", line 347, in <genexpr>
    return (item for chunk in result for item in chunk)
  File "/opt/python/3.6.3/lib/python3.6/multiprocessing/pool.py", line 735, in next
    raise value
IndexError: list index out of range

opened by The-Compiler 10

Add option to ignore certain builtins

flake8-builtins complains about variables named license, which honestly I don't understand why it even exists outside of the REPL. I don't want to rename them to lic, licence, licence_ or similar, so it would be nice to not have to sprinkle my code with # noqa everywhere.

opened by 0xallie 8

Tuple unpacking breaks this plugin

Code

Valid python code break this linter with an exception.

>>> a, *(b, c) = 1, 2, 3
>>> print(a, b, c)
1 2 3

Problem

Reproduction:

# test.py
a, *(b, c) = 1, 2, 3

Run: flake8 test.py Output:

» flake8 test.py
Traceback (most recent call last):
  File "/Users/sobolev/Documents/github/wemake-python-styleguide/.venv/bin/flake8", line 10, in <module>
    sys.exit(main())
  File "/Users/sobolev/Documents/github/wemake-python-styleguide/.venv/lib/python3.7/site-packages/flake8/main/cli.py", line 18, in main
    app.run(argv)
  File "/Users/sobolev/Documents/github/wemake-python-styleguide/.venv/lib/python3.7/site-packages/flake8/main/application.py", line 393, in run
    self._run(argv)
  File "/Users/sobolev/Documents/github/wemake-python-styleguide/.venv/lib/python3.7/site-packages/flake8/main/application.py", line 381, in _run
    self.run_checks()
  File "/Users/sobolev/Documents/github/wemake-python-styleguide/.venv/lib/python3.7/site-packages/flake8/main/application.py", line 300, in run_checks
    self.file_checker_manager.run()
  File "/Users/sobolev/Documents/github/wemake-python-styleguide/.venv/lib/python3.7/site-packages/flake8/checker.py", line 331, in run
    self.run_serial()
  File "/Users/sobolev/Documents/github/wemake-python-styleguide/.venv/lib/python3.7/site-packages/flake8/checker.py", line 315, in run_serial
    checker.run_checks()
  File "/Users/sobolev/Documents/github/wemake-python-styleguide/.venv/lib/python3.7/site-packages/flake8/checker.py", line 598, in run_checks
    self.run_ast_checks()
  File "/Users/sobolev/Documents/github/wemake-python-styleguide/.venv/lib/python3.7/site-packages/flake8/checker.py", line 502, in run_ast_checks
    for (line_number, offset, text, check) in runner:
  File "/Users/sobolev/Documents/github/wemake-python-styleguide/.venv/lib/python3.7/site-packages/flake8_builtins.py", line 106, in run
    for line, offset, msg, rtype in value:
  File "/Users/sobolev/Documents/github/wemake-python-styleguide/.venv/lib/python3.7/site-packages/flake8_builtins.py", line 124, in check_assignment
    item.value.id in BUILTINS:
AttributeError: 'Tuple' object has no attribute 'id'

Versions:

python3.7
flake8: 3.7.8
flake8-builtins: 1.4.1

opened by sobolevn 8

Fix/tuple parsing

This PR attempts to fix https://github.com/gforcada/flake8-builtins/issues/40.

I added the test case mentioned and fixed the issue. Also, added a library called hypothesmith which generates thousands of parseable python programs. Because of this, I was able to find the same issue in the for loop code. If you like, you can cherry-pick flake8_builtins.py or include the new test and dependencies.

Note, I had to update pytest, pluggy and attrs in the dev-dependencies.

Happy holidays!

opened by memery-rbx 7

`AttributeError` seen with versions 1.2.0 and 1.2.1

With version flake8-builtins 1.2.0 and later I'm seeing the following issue while running flake8. It works fine with flake8-builtins 1.1.1.

Using python 2.7.14

[root@532b769a6003 /]# flake8 src/
Traceback (most recent call last):
  File "/opt/stackstorm/virtualenvs/stackstorm/bin/flake8", line 11, in <module>
    sys.exit(main())
  File "/opt/stackstorm/virtualenvs/stackstorm/lib/python2.7/site-packages/flake8/main/cli.py", line 16, in main
    app.run(argv)
  File "/opt/stackstorm/virtualenvs/stackstorm/lib/python2.7/site-packages/flake8/main/application.py", line 328, in run
    self._run(argv)
  File "/opt/stackstorm/virtualenvs/stackstorm/lib/python2.7/site-packages/flake8/main/application.py", line 316, in _run
    self.run_checks()
  File "/opt/stackstorm/virtualenvs/stackstorm/lib/python2.7/site-packages/flake8/main/application.py", line 246, in run_checks
    self.file_checker_manager.run()
  File "/opt/stackstorm/virtualenvs/stackstorm/lib/python2.7/site-packages/flake8/checker.py", line 317, in run
    self.run_parallel()
  File "/opt/stackstorm/virtualenvs/stackstorm/lib/python2.7/site-packages/flake8/checker.py", line 286, in run_parallel
    for ret in pool_map:
  File "/opt/python/lib/python2.7/multiprocessing/pool.py", line 289, in <genexpr>
    return (item for chunk in result for item in chunk)
  File "/opt/python/lib/python2.7/multiprocessing/pool.py", line 673, in next
    raise value
AttributeError: 'Attribute' object has no attribute 'id'

opened by tim-ireland 7

Major cleanup: python versions, versions pinned and github actions
Finally I have some time to spend on setting a new base for flake8-builtins future ✨

python 2.7 and 3.6 support was removed, which allows to remove quite some code

version pins on requirements.txt were updated, which will remove the security warnings GitHub is displaying

GitHub actions was updated, to ensure the supported python versions are actually working

I always like to create lots of commits with each doing one specific topic, so although the changes are quite a lot, they are all (hopefully) isolated 🤞🏾 😄

@cclauss @gsingh93 you might want to have a look. I will review and merge your PR on top of this one, if I manage to make this one pass CI, my skills level on GitHub actions is rather low 😓 today is already improving this 😄
opened by gforcada 5

Does not recognize additional --builtins

As per the docs, it is possible to add builtins to flake8 by passing the --builtins flag or through config files.

However, these are not recognized by flake8-builtins:

import gettext

gettext.install("minimal_repro")


def id(s):
    return s


def _(s):
    return s


print(id("foo"))
print(_("bar"))

$ python ./no_custom_builtins.py
foo
bar
$ flake8 ./no_custom_builtins.py --builtins=_
./no_custom_builtins.py:1:1: D100 Missing docstring in public module
./no_custom_builtins.py:6:1: A001 variable "id" is shadowing a python builtin
./no_custom_builtins.py:6:1: D103 Missing docstring in public function

A001 should be reported for both functions.

opened by kthy 5

Remove '_' from the builtins list
After upgrading to the latest version, I have faced this issue:

/Users/.../user_details_step.py:3:1: A001 "_" is a python builtin and is being shadowed, consider renaming the variable

But _ is a common name for unused variables, I think it is not right to annotate them with # noqa.
opened by sobolevn 5
False negative in some control flows
Given this code sample:

try: 1 / 0 except ZeroDivisionError as sum: print(sum)

This should rise an error. But it does not. That's a bug, I guess.

I will create a PR with the test after #15 will be merged.
opened by sobolevn 5

Broken under SublimeLinter-flake8

Commit 628e988459fd827e4960ea82a397a08914a5de23 broke flake8-builtins when running in SublimeText under SublimeLinter and SublimeLinter-flake8. This causes flake8 linting to stop working entirely in the editor as an exception is thrown during linting.

Traceback (most recent call last):
  File "~/.virtualenvs/linting/bin/flake8", line 11, in <module>
    sys.exit(main())
  File "~/.virtualenvs/linting/lib/python2.7/site-packages/flake8/main.py", line 36, in main
    report = flake8_style.check_files()
  File "~/.virtualenvs/linting/lib/python2.7/site-packages/flake8/engine.py", line 181, in check_files
    return self._retry_serial(self._styleguide.check_files, paths=paths)
  File "~/.virtualenvs/linting/lib/python2.7/site-packages/flake8/engine.py", line 172, in _retry_serial
    return func(*args, **kwargs)
  File "~/.virtualenvs/linting/lib/python2.7/site-packages/pycodestyle.py", line 1877, in check_files
    runner(path)
  File "~/.virtualenvs/linting/lib/python2.7/site-packages/flake8/engine.py", line 126, in input_file
    return fchecker.check_all(expected=expected, line_offset=line_offset)
  File "~/.virtualenvs/linting/lib/python2.7/site-packages/pycodestyle.py", line 1608, in check_all
    self.check_ast()
  File "~/.virtualenvs/linting/lib/python2.7/site-packages/pycodestyle.py", line 1555, in check_ast
    for lineno, offset, text, check in checker.run():
  File "~/.virtualenvs/linting/lib/python2.7/site-packages/flake8_builtins.py", line 54, in run
    tree = ast.parse(lines)
  File "/usr/local/Cellar/python/2.7.12/Frameworks/Python.framework/Versions/2.7/lib/python2.7/ast.py", line 37, in parse
    return compile(source, filename, mode, PyCF_ONLY_AST)
TypeError: expected a readable buffer object

I'm not sure exactly what is going wrong here, but apparently dropping the lines added in the commit fixes the issue. I don't want to just make a PR for this though, as I'm sure I'm missing some detail as to why it was added in the first place.

opened by danpalmer 5

A003 should be disabled by default
Consider the following example:

class User(Model): id: str def __str__(self): return f"User(id:{self.id})" user = User(id='123') print(user.id)

Class attributes are almost never accessed by themselves without going through an object or a class, so what's the point of this rule? If you must preserve this rule, please disable it by default.
opened by wyuenho 6