python 函数

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,]