python中的特殊函數__call__()以及init,setattr,getattr,delattr

有關python的call在官方文檔上有這麼一句解釋 (call#object.call“>http://docs.python.org/reference/datamodel.html?highlight=call#object.call)

object.call(self[, args…])

Called when the instance is “called” as a function; if this method is defined, x(arg1, arg2, …) is a shorthand for x.call(arg1, arg2, …).

當把一個執行個體當作方法來調用的時候，形如instance(arg1,args2,…)，那麼實際上調用的就是 instance.call(arg1,arg2,…)

class A:
    def __init__(self):
        print "__init__ method"
    def __call__(self):
        print "__call__ method"

a = A()
#__init__ method
a()
#__call__ method
           

其他特殊函數的功能如下，用代碼說話

class A(object):
    def __init__(self, arg):
        print "__init__ method", arg
    def __call__(self, arg):
        print "__call__ method", arg
    def __setattr__(self, key, value):
        print "__setattr__ method", key, value
    def __getattr__(self, key):
        print "__getattr__ method", key
    def __delattr__(self, key):
        print "__delattr__ method", key

a = A('1')
# __init__ method 1
a('2')
# __call__ method 2
a.attr = '3'
# __setattr__ method attr 3
a.attr
# __getattr__ method attr
del a.attr
# __delattr__ method attr