Consider using identity comparison with singleton PTC-W0068
Bug risk
Major
6 months ago
—
a year old
Comparison to singleton
False should be expr is False121 assert data['path'] == path
122 assert data['isDir'] == False
123 assert data['isFile'] == True
124 assert data['isLink'] == False125 assert data['mode'] == 0o100765
126 assert data['uid'] == os.stat(path).st_uid
127 assert data['gid'] == os.stat(path).st_gidComparison to singleton
True should be expr is True120 assert data['name'] == 'file'
121 assert data['path'] == path
122 assert data['isDir'] == False
123 assert data['isFile'] == True124 assert data['isLink'] == False
125 assert data['mode'] == 0o100765
126 assert data['uid'] == os.stat(path).st_uidComparison to singleton
False should be expr is False119 data = rq.json()
120 assert data['name'] == 'file'
121 assert data['path'] == path
122 assert data['isDir'] == False123 assert data['isFile'] == True
124 assert data['isLink'] == False
125 assert data['mode'] == 0o100765Comparison to singleton
False should be expr is False101 assert data[0]['path'] == path
102 assert data[0]['isDir'] == False
103 assert data[0]['isFile'] == True
104 assert data[0]['isLink'] == False105 assert data[0]['mode'] == 0o100765
106 assert data[0]['uid'] == os.stat(path).st_uid
107 assert data[0]['gid'] == os.stat(path).st_gidComparison to singleton
True should be expr is True100 assert data[0]['name'] == 'file'
101 assert data[0]['path'] == path
102 assert data[0]['isDir'] == False
103 assert data[0]['isFile'] == True104 assert data[0]['isLink'] == False
105 assert data[0]['mode'] == 0o100765
106 assert data[0]['uid'] == os.stat(path).st_uid
Description
Comparisons to the singleton objects, like True, False, and None, should be done with identity, not equality. Use is or is not.
Identity checks are faster than equality checks.
Also, the equality checks can result in unintended behaviour in some cases:
>>> 1 is True
False
>>> 1 == True
True
>>> 1.0 is True
False
>>> 1.0 == True
True
Bad practice
value = fx()
if value == True: # `==` can cause unintended behaviour
print(value)
if value != None:
print(value)
Recommended
value = fx()
if value is True: # `is` for Identity comparison
print(value)
if value is not None:
print(value)
Exceptions:
Equality comparisons might be required in some cases, especially in SQLAlchemy, SQLObject, ORMs, etc. In these cases, it is safe to ignore this issue.