darkfirefly

    >>> def function(b, a=[]):
    ...     a.append(b)
    ...     print(a)
    ... 
    ...     
    >>> function(1)
    [1]
    >>> function(2)
    [1, 2]
    >>> function(3, [4])
    [4, 3]
    >>> function(5)
    [1, 2, 5]

    >>> def function2(b, a=None):
    ...     if a is None: a = []
    ...     a.append(b)
    ...     print(a)