This is addressed in the FAQ.
http://www.python.org/doc/faq/general/#why-are-default-values-shared-between-objects
jitendra gupta wrote:
def foo(x = [0]):
x[0] = x[0] + 1
return x[0]
def soo(x = None):
if x is None:
x = [0]
x[0] = x[0] + 1
return x[0]
>>> foo()
1
>>>foo() #See the behavior incremented by one
2
>>>foo([1]) # but here based on given number
2
>>>foo()
3
>>>foo([1])
2
>>>foo()
4
>>>soo()
1
>>>soo()
1
>>>soo([1])
2
>>>soo()
1
Why foo() is incremented by 1 always when we are not passing any argument,
but this is not happening in soo() case, In which scenario
we will use these type of function.'
Thanks
Jitendra Kumar
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