#!/usr/bin/env python
# -*- coding: utf-8 -*-
#python2.7x
#partial.py
#authror: orangleliu

'''
functools 中Partial可以用來(lái)改變一個(gè)方法默認(rèn)參數(shù)
1 改變?cè)心J(rèn)值參數(shù)的默認(rèn)值
2 給原來(lái)沒(méi)有默認(rèn)值的參數(shù)增加默認(rèn)值
'''
def foo(a,b=0) :
??? '''
??? int add'
??? '''
??? print a + b

#user default argument
foo(1)

#change default argument once
foo(1,1)

#change function's default argument, and you can use the function with new argument
import functools

foo1 = functools.partial(foo, b=5)? #change "b" default argument
foo1(1)

foo2 = functools.partial(foo, a=10) #give "a" default argument
foo2()

'''
foo2 is a partial object,it only has three read-only attributes
i will list them
'''
print foo2.func
print foo2.args
print foo2.keywords
print dir(foo2)

##默認(rèn)情況下partial對(duì)象是沒(méi)有 __name__ __doc__ 屬性，使用update_wrapper 從原始方法中添加屬性到partial 對(duì)象中
print foo2.__doc__
'''
執(zhí)行結(jié)果：
partial(func, *args, **keywords) - new function with partial application
??? of the given arguments and keywords.
'''

functools.update_wrapper(foo2, foo)
print foo2.__doc__
'''
修改為foo的文檔信息了
'''