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allow is and is not for type comparisons (E721) #1086

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Jul 15, 2023
Merged

allow is and is not for type comparisons (E721) #1086

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9f6a181
Revert "Merge pull request #1085 from PyCQA/revert-1041"
asottile Jul 30, 2022
ac223bd
allow `is` and `is not` for type compares
asottile Jul 30, 2022
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15 changes: 5 additions & 10 deletions pycodestyle.py
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Original file line number Diff line number Diff line change
Expand Up @@ -128,8 +128,10 @@
r'\s*(?(1)|(None|False|True))\b')
COMPARE_NEGATIVE_REGEX = re.compile(r'\b(?<!is\s)(not)\s+[^][)(}{ ]+\s+'
r'(in|is)\s')
COMPARE_TYPE_REGEX = re.compile(r'(?:[=!]=|is(?:\s+not)?)\s+type(?:s.\w+Type'
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I can't find the rationale for removing types.*Type comparisons in the linked issues. As far as I can tell, those should still be included in the checks, shouldn't they?

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I think those got removed because the name types isn't necessarily the stdlib types module -- not 100% sure though

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the original patch is here: #1041 -- this is just a revert-revert of that with an additional commit on top

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I suppose the precise reasoning is the following, then:

This check also breaks many ligimitate cases (such as having your own types module with an Enum class for instance, and comparing a value to the enum member).

which I can relate to. You can, of course, also shadow the built-in type function, but that's just not something people do in general and having a custom types module is much more likely, although also ending your enum in Type is most likely less common.

r'|\s*\(\s*([^)]*[^ )])\s*\))')
COMPARE_TYPE_REGEX = re.compile(
r'[=!]=\s+type(?:\s*\(\s*([^)]*[^ )])\s*\))'
r'|\btype(?:\s*\(\s*([^)]*[^ )])\s*\))\s+[=!]='
)
KEYWORD_REGEX = re.compile(r'(\s*)\b(?:%s)\b(\s*)' % r'|'.join(KEYWORDS))
OPERATOR_REGEX = re.compile(r'(?:[^,\s])(\s*)(?:[-+*/|!<=>%&^]+|:=)(\s*)')
LAMBDA_REGEX = re.compile(r'\blambda\b')
Expand Down Expand Up @@ -1457,14 +1459,7 @@ def comparison_type(logical_line, noqa):
Do not compare types directly.

Okay: if isinstance(obj, int):
E721: if type(obj) is type(1):

When checking if an object is a string, keep in mind that it might
be a unicode string too! In Python 2.3, str and unicode have a
common base class, basestring, so you can do:

Okay: if isinstance(obj, basestring):
Okay: if type(a1) is type(b1):
E721: if type(obj) == type(1):
"""
match = COMPARE_TYPE_REGEX.search(logical_line)
if match and not noqa:
Expand Down
15 changes: 9 additions & 6 deletions testsuite/E72.py
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Original file line number Diff line number Diff line change
Expand Up @@ -4,12 +4,12 @@
#: E721
if type(res) != type(""):
pass
#: E721
#: Okay
import types

if res == types.IntType:
pass
#: E721
#: Okay
import types

if type(res) is not types.ListType:
Expand All @@ -26,9 +26,9 @@
assert type(res) == type((0))
#: E721
assert type(res) != type((1, ))
#: E721
#: Okay
assert type(res) is type((1, ))
#: E721
#: Okay
assert type(res) is not type((1, ))
#: E211 E721
assert type(res) == type ([2, ])
Expand All @@ -47,8 +47,6 @@
pass
if isinstance(res, types.MethodType):
pass
if type(a) != type(b) or type(a) == type(ccc):
pass
#: Okay
def func_histype(a, b, c):
pass
Expand Down Expand Up @@ -81,6 +79,11 @@ def func_histype(a, b, c):
except Exception:
pass
#: Okay
from . import custom_types as types

red = types.ColorTypeRED
red is types.ColorType.RED
#: Okay
from . import compute_type

if compute_type(foo) == 5:
Expand Down