Strange Python behavior from inappropriate usage of 'is not' comparison?

Question

I (incorrectly?) used \'is not\' in a comparison and found this curious behavior:

>>> a = 256
>>> b = int(\'256\')
>>> c = 300
>>         


        

Answer 1

Int is an object in python, and python caches small integer between [-5,256] by default, so where you use int in [-5,256], they are identical.

a = 256
b = 256

a is b # True

If you declare two integers not in [-5,256], python will create two objects which are not the same(though they have the same value).

a = 257
b = 257

a is b # False

In your case, using != instead to compare the value is the right way.

a = 257
b = 257

a != b # False