Simple strange basic python behaviour

Question

Does anybody know why this below code prints 0 and 1 rather than 5 and 2, in csharp similar code would print 5 and 2 and I am just trying to work out the logic here.

class Myclass:
 a = 0
 b = 1 
def foo():
 for x in range(1):
 for y in range(1):
 myclass = Myclass()
 if y == 1:
 myclass.a = 5
 if y == 1:
 myclass.b = 2
 ClassList.append(Myclass)
 for x in ClassList:
 print x.a 
 print x.b
ClassList = []
foo() 

• Pradyumna: at the end y=0 cause range(1) returns [0] and x is myclass

Answer 1

Because y is never 1:

>>> range(1)
[0]

What you want is range(2)

And just incase you are not aware... currently you are using a and b as class attributes as opposed to instance attributes. For your specific case of doing value assignments, you won't see a problem, but if you were to have defined say, dictionaries or lists, and were changing keys/indices of those objects, it would be the same object shared across all of the instances.

class Myclass(object):
 a = []
 b = {}
obj1 = Myclass()
obj2 = Myclass()
obj1.a.append('foo')
obj1.b['biz'] = 'baz'
print obj2.a
# ['foo']
print obj2.b
# {'biz': 'baz'}

... vs instance attributes

class Myclass(object):
 def __init__(self):
 self.a = []
 self.b = {}

• Dolda2000: "This means settings myclass.a = 5 will set it for the entire class, shared." <-- This is not true. Evaluating myclass.a = 5 will always modify the instance's __dict__, regardless of whether the name is defined in the class' __dict__ or not.
• jdi: I was just about to delete that. int is immutable. If OP were using a list or dict it would matter.
• Dolda2000: No, it would still not matter.
• jdi: I understand you mean assignments. I am simply pointing out that the OP is using class attributes in case they were not aware. Doing something like myclass.aDict['foo'] = 'bar' would be shared among all the instances.
• Dolda2000: Sure enough, that is true. Not because int is immutable, though.

Answer 2

The reason is that range(1) returns [0], not [0, 1], so your y == 1 test never evaluates to true.

Also, you're appending Myclass rather than myclass -- that is, the actual class, rather than the instance you created -- to the list, so you're always printing the unmodified a and b from the class.