def extendList(val, list=[]):
    list.append(val)
    return list
list1 = extendList(10)
list2 = extendList(123,[])
list3 = extendList('a')
print ("list1 = %s" % list1)
print ("list2 = %s" % list2)
print ("list3 = %s" % list3)



def extendList(val, list=None):
  if list is None:
    list = []
  list.append(val)
  return list
list1 = extendList(10)
list2 = extendList(123,[])
list3 = extendList('a')
print ("list1 = %s" % list1)
print ("list2 = %s" % list2)
print ("list3 = %s" % list3)