python apply()函数

>>> help(apply)
Help on built-in function apply in module __builtin__:
apply(...)
    apply(object[, args[, kwargs]]) -> value
    Call a callable object with positional arguments taken from the tuple args,
    and keyWord arguments taken from the optional dictionary kwargs.
    Note that classes are callable, as are instances with a __call__() method.
    <span style="color:#ff0000;">Deprecated since release 2.3. Instead, use the extended call syntax:
        function(*args, **keywords).</span>
>>> 

args是一个包含将要提供给函数的按位置传递的参数的元组。如果省略了args，任何参数都不会被传递。
kwargs是一个包含关键字参数的字典。
apply()的返回值就是object()的返回值。
apply()的元素参数是有序的，元素的顺序必须和object()形式参数的顺序一致。

1》执行不带参数的函数

def say():
    print 'hello python!'
    
say()
apply(say)

结果：
hello Python!
hello python!
2》函数只带元组的参数

def say(a):
    print a

say('hello python!')
apply(say,("hello python!",))

def say_again(a,b):
    print a,b

say_again('hello','python!')
apply(say_again,('hello','python!'))

结果：
hello python!
hello python!
hello python!
hello python!
3》函数带关键字参数

def say(a=1,b=2):
    print a,b
 
def haha(**kw):
    print kw
    print type(kw)
    say()
    say(kw)#将kw传给a, b取默认值
    apply(say,(),kw)
 
haha(a='hello',b='python!')

结果：
{'a': 'hello', 'b': 'python!'}
<type 'dict'>
1 2
{'a': 'hello', 'b': 'python!'} 2

hello python!

又如：

def say(x,y,a=1,b=2):  
    print x,y,a,b  
   
def haha(*args,**kw):
    print args,type(args)
    print kw,type(kw)
    apply(say,args,kw)  
   
haha(1,2,a='hello',b='python!')  

结果：

(1, 2) <type 'tuple'>
{'a': 'hello', 'b': 'python!'} <type 'dict'>
1 2 hello python!