Python参数传递采用的肯定是“传对象引用”的方式。这种方式相当于传值和传引用的一种综合。如果函数收到的是一个可变对象（比如字典或者列表）的引用，就能修改对象的原始值－－相当于通过“传引用”来传递对象。如果函数收到的是一个不可变对象（比如数字、字符或者元组）的引用，就不能直接修改原始对象－－相当于通过“传值'来传递对象。
列表，字典等参数: 传引用，函数中对这些对象做修改，原来的值也会被修改。
int，string, tuple: 传引用，但是结果像传值，函数的修改不会反映到原变量。
#!/usr/bin/python
# -*- coding: utf-8 -*- a = {i: i*i for i in range(10)}
b = 10
c = "hello world!" def pop_list(x):
for i in range(len(x)):
x.pop(i)
print x def decrease(y):
y = y-2
print y def slice(string):
string = string[:2]
print string if __name__ == "__main__":
print "-" * 10 + "original a" + "-" * 10
print a
print "-"*10 + "params in function" + "-"*10
pop_list(a)
print "-" * 10 + "a" + "-" * 10
print a print "-" * 10 + "original b" + "-" * 10
print b
print "-" * 10 + "params in function" + "-" * 10
decrease(b)
print "-" * 10 + "b" + "-" * 10
print b print "-" * 10 + " original c" + "-" * 10
print c
print "-" * 10 + "params in function" + "-" * 10
slice(c)
print "-" * 10 + "c" + "-" * 10
print c
output:
----------original a----------
{0: 0, 1: 1, 2: 4, 3: 9, 4: 16, 5: 25, 6: 36, 7: 49, 8: 64, 9: 81}
----------params in function----------
{}
----------a----------
{}
----------original b----------
10
----------params in function----------
8
----------b----------
10
---------- original c----------
hello world!
----------params in function----------
he
----------c----------
hello world!
ref: http://www.cnblogs.com/loleina/p/5276918.html