2.1.2.5 函数废弃

假如我们想要在我们不再喜欢的函数第一次激活时在stderr打印废弃警告。如果我们不像修改函数，那么我们可以使用修饰器：

In [16]:

class deprecated(object):
    """Print a deprecation warning once on first use of the function.
 >>> @deprecated()                    # doctest: +SKIP
 ... def f():
 ...     pass
 >>> f()                              # doctest: +SKIP
 f is deprecated
 """
    def __call__(self, func):
        self.func = func
        self.count = 0
        return self._wrapper
    def _wrapper(self, *args, **kwargs):
        self.count += 1
        if self.count == 1:
            print self.func.__name__, 'is deprecated'
        return self.func(*args, **kwargs)

也可以将其实施为一个函数：

In [17]:

def deprecated(func):
    """Print a deprecation warning once on first use of the function.
 >>> @deprecated                      # doctest: +SKIP
 ... def f():
 ...     pass
 >>> f()                              # doctest: +SKIP
 f is deprecated
 """
    count = [0]
    def wrapper(*args, **kwargs):
        count[0] += 1
        if count[0] == 1:
            print func.__name__, 'is deprecated'
        return func(*args, **kwargs)
    return wrapper