Consider using identity comparison with singleton PTC-W0068
Bug risk
Major
3 years ago
—
3 years old
Comparison to singleton
None should be expr is None116 # getting a particular sheet by name out of many sheets
117
118 student_batch = request.POST['batch']
119 if student_batch == None:120 student_batch = 2016
121 worksheet = wb["BATCH " + str(student_batch)]
122 print(worksheet)Comparison to singleton
None should be expr is not None129 section = list()
130 instructor = list()
131 for col in worksheet['C']:
132 if(col.value != None):133 code.append(col.value)
134 for col in worksheet['D']:
135 if(col.value != None):Comparison to singleton
None should be expr is not None132 if(col.value != None):
133 code.append(col.value)
134 for col in worksheet['D']:
135 if(col.value != None):136 title.append(col.value)
137 for col in worksheet['E']:
138 if(col.value != None):Comparison to singleton
None should be expr is not None135 if(col.value != None):
136 title.append(col.value)
137 for col in worksheet['E']:
138 if(col.value != None):139 short.append(col.value)
140 for col in worksheet['G']:
141 if(col.value != None):Comparison to singleton
None should be expr is not None138 if(col.value != None):
139 short.append(col.value)
140 for col in worksheet['G']:
141 if(col.value != None):142 crdthr.append(col.value)
143
144 for col in worksheet['I']:
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.