flake8-comprehensions 1.3.0

A flake8 plugin to help you write better list/set/dict comprehensions.

flake8-comprehensions

A flake8 plugin that helps you write better list/set/dict comprehensions.

• Free software: ISC license

Installation

Install from pip with:

pip install flake8-comprehensions

It will then automatically be run as part of flake8; you can check it has been picked up with:

$ flake8 --version
2.4.1 (pep8: 1.7.0, pyflakes: 0.8.1, flake8-comprehensions: 1.0.0, mccabe: 0.3.1) CPython 2.7.11 on Darwin

Rules

Code	Rule
C400	Unnecessary generator - rewrite as a list comprehension.
C401	Unnecessary generator - rewrite as a set comprehension.
C402	Unnecessary generator - rewrite as a dict comprehension.
C403	Unnecessary list comprehension - rewrite as a set comprehension.
C404	Unnecessary list comprehension - rewrite as a dict comprehension.
C405	Unnecessary (list/tuple) literal - rewrite as a set literal.
C406	Unnecessary (list/tuple) literal - rewrite as a dict literal.
C407	Unnecessary list comprehension - ‘<builtin>’ can take a generator.

Examples

C400-402: Unnecessary generator

It’s unnecessary to use list, set, or dict around a generator expression, since there are equivalent comprehensions for these types. For example:

• list(f(x) for x in foo) is better as [f(x) for x in foo]

• set(f(x) for x in foo) is better as {f(x) for x in foo}

• dict((x, f(x)) for x in foo) is better as {x: f(x) for x in foo}

C403-404: Unnecessary list comprehension

It’s unnecessary to use a list comprehension inside a call to set or dict, since there are equivalent comprehensions for these types. For example:

• set([f(x) for x in foo]) is better as {f(x) for x in foo}

• dict([(x, f(x)) for x in foo]) is better as {x: f(x) for x in foo}

C405-406: Unnecessary list literal

It’s unnecessary to use a list literal within a call to set or dict since there is literal syntax for these types. For example:

• set([1, 2]) is better as {1, 2}

• set([]) is better as set()

• dict([]) is better as {}

• dict([(1, 2)]) is better as {1: 2}

• dict(((1, 2),)) is better as {1: 2}

C407: Unnecessary list comprehension - ‘<builtin>’ can take a generator

It’s unnecessary to pass a list comprehension to some builtins that can take generators instead. For example:

• sum([x ** 2 for x in range(10)]) is better as sum(x ** 2 for x in range(10))

• all([foo.bar for foo in foos]) is better as all(foo.bar for foo in foos)

The list of builtins that are checked for are:

• all

• any

• frozenset

• max

• min

• sorted

• sum

• tuple

History

Pending Release

1.3.0 (2017-05-01)

• Don’t allow installation with Flake8 3.2.0 which doesn’t enable the plugin. This bug was fixed in Flake8 3.2.1.

• Prevent false positives of C402 from generators of expressions that aren’t two-tuples.

• C405 and C406 now also complain about unnecessary tuple literals.

1.2.1 (2016-06-27)

• C407 rule that complains about unnecessary list comprehensions inside builtins that can work on generators.

1.2.0 (2016-07-11)

• Split all rule codes by type. This allows granular selection of the rules in flake8 configuration.

1.1.1 (2016-04-06)

• Fix crash on method calls

1.1.0 (2016-04-06)

• C401 rule that complains about unnecessary list comprehensions inside calls to set() or dict().

• C402 rule that complains about unnecessary list literals inside calls to set() or dict().

1.0.0 (2016-04-05)

• C400 rule that complains about an unnecessary usage of a generator when a list/set/dict comprehension would do.