Consider using identity comparison with singleton PTC-W0068
Bug risk
Major
10 months ago
—
10 months old
Comparison to singleton
None should be expr is None460 return totalcost
461
462 def canBeExtended(self, max_cost=None):
463 if max_cost == None:464 max_cost = self.max_cost
465 return self.cost() < max_cost
466Comparison to singleton
None should be expr is not None279
280 def copy(self):
281 gdgtCpy = GadgetMatrix(self.arch)
282 if self.chainCond != None:283 gdgtCpy.chainCond = self.chainCond.copy()
284 gdgtCpy.matrix = self.matrix.copy()
285 gdgtCpy.inst = self.instComparison to singleton
None should be expr is None267 instMatrix = self.lookupFromCache(inst)
268
269 # init chain cond or update
270 if self.chainCond == None:271 self.initChainCond(inst)
272 else:
273 # TODO: Hypothesis no side effect on chainInstComparison to singleton
None should be expr is None216
217 def initChainCond(self, chainInst):
218
219 if self.inst == None:220 self.inst = chainInst
221 self.matrix = sparse.identity(self.arch.size, dtype=bool).tocsr()
222 # groups = chainInst.groupsComparison to singleton
None should be expr is not None211 self.nbrInsts = 0
212 self.nbrBytes = 0
213
214 if chainInst != None:215 self.addInst(chainInst)
216
217 def initChainCond(self, chainInst):
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.