unnecessary-generator-list (C400)

Derived from the flake8-comprehensions linter.

Fix is always available.

What it does

Checks for unnecessary generators that can be rewritten as list comprehensions (or with list() directly).

Why is this bad?

It is unnecessary to use list() around a generator expression, since there are equivalent comprehensions for these types. Using a comprehension is clearer and more idiomatic.

Further, if the comprehension can be removed entirely, as in the case of list(x for x in foo), it's better to use list(foo) directly, since it's even more direct.

Example

list(f(x) for x in foo)
list(x for x in foo)
list((x for x in foo))

Use instead:

[f(x) for x in foo]
list(foo)
list(foo)

Fix safety

This rule's fix is marked as unsafe, as it may occasionally drop comments when rewriting the call. In most cases, though, comments will be preserved.