Possible Duplicate:
“Least Astonishment” in Python: The Mutable Default Argument
can anyone explain me this?
class Strange(object):
def mutate(self, x=[]):
x.append(1)
return x
obj = Strange()
print obj.mutate()
another_obj = Strange()
print another_obj.mutate()
>> [1]
>> [1, 1]
mutate() is called without the optional parameter. shouldn't x then always be []? what confuses me also is that the value of x is also shared across different objects...
