>>def addToList(val, list=[]):

>> list.append(val)

>> return list

>>list1 = addToList(1)

>>list2 = addToList(123,[])

>>list3 = addToList('a’)

>>print ("list1 = %s" % list1)

>>print ("list2 = %s" % list2)

>>print ("list3 = %s" % list3)

Output:

list1 = [1,’a’]

list2 = [123]

lilst3 = [1,’a’]

Note that list1 and list3 are equal. When we passed the information to the addToList, we did it without a second value. If we don't have an empty list as the second value, it will start off with an empty list, which we then append. For list2, we appended the value to an empty list, so its value becomes [123].

For list3, we're adding ‘a’ to the list. Because we didn't designate the list, it is a shared value. It means the list doesn’t reset and we get its value as [1, ‘a’].

Remember that a default list is created only once during the function and not during its call number.