python 为什么调用函数会令引用计数+2

Question

import sys
a = 11
init_cnt = sys.getrefcount(a) - 1

print "init", init_cnt
####init 22
def function(c):
    print 'in function, count: ', sys.getrefcount(c) - 1
    ####in function, count:  24
    print '函数调用，计数器增加', sys.getrefcount(c) - 1 - init_cnt
    ####函数调用，计数器增加 2
function(a)

Answer 1

After passing a as a parameter to function, it is referenced twice:

for attr in dir(function):
    print attr, getattr(function, attr)

You can see that parameter a is referenced by two attributes in the function object.