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

'''
functools 中Partial可以用來改變一個方法默認參數
1 改變原有默認值參數的默認值
2 給原來沒有默認值的參數增加默認值
'''
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)

##默認情況下partial對象是沒有 __name__ __doc__ 屬性，使用update_wrapper 從原始方法中添加屬性到partial 對象中
print foo2.__doc__
'''
執行結果：
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
'''