def f2 (arg): if len(arg)>2: del arg[2:] li = [11,22,33,44] f2(li) print(li)
>>> [11,22]
def f3 (arg): arg=123 li=[11,22,33,44] f3(li) print(li)
实际运算是
arg=li
arg=123
所以输出是[11,22,33,44,]