python classmethod staticmethod

Love The Way You Lie 2022-08-06 09:19 157阅读 0赞

classmethod ( *function* )

Return a class method for *function*.

A class method receives the class as implicit first argument, just like an instance method receives the instance. To declare a class method, use this idiom:

class C(object):
        @classmethod
        def f(cls, arg1, arg2, ...):
            ...

It can be called either on the class (such as C.f()) or on an instance (such asC().f()). The instance is ignored except for its class. If a class method is called for a derived class, the derived class object is passed as the implied first argument.

staticmethod ( *function* )

Return a static method for *function*.

A static method does not receive an implicit first argument. To declare a static method, use this idiom:

class C(object):
        @staticmethod
        def f(arg1, arg2, ...):
            ...

It can be called either on the class (such as C.f()) or on an instance (such asC().f()). The instance is ignored except for its class.

Static methods in Python are similar to those found in Java or C++.

在下面的实例中，重点是cls(value)

>>> class co(object):
        def __init__(self, str='ok'):
            self.str = str
            print 'init ok'
        @classmethod
        def from_dict(cls, values):
            return cls(values)
        @classmethod
        def from_none(cls):
            return cls()
    
        
    >>> co.from_none()
    init ok
    <__main__.co object at 0x0000000002FEC470>
    >>> co.from_none().str
    init ok
    'ok'
    >>> co.from_dict('aaa')
    init ok
    <__main__.co object at 0x0000000002FEC668>
    >>> co.from_dict('aaa').str
    init ok
    'aaa'
    >>>

参考：

http://luozhaoyu.iteye.com/blog/1506376

http://blog.csdn.net/lovingprince/article/details/6595466