Python:为什么我不能让我的装饰器工作？

Question

现在这对那些刚接触这个问题的人有效:

class ensureparams(object):
    """

    Used as a decorator with an iterable passed in, this will look for each item
    in the iterable given as a key in the params argument of the function being
    decorated. It was built for a series of PayPal methods that require
    different params, and AOP was the best way to handle it while staying DRY.


    >>> @ensureparams(['name', 'pass', 'code'])
    ... def complex_function(params):
    ...     print(params['name'])
    ...     print(params['pass'])
    ...     print(params['code'])
    >>> 
    >>> params = {
    ...     'name': 'John Doe',
    ...     'pass': 'OpenSesame',
    ...     #'code': '1134',
    ... }
    >>> 
    >>> complex_function(params=params)
    Traceback (most recent call last):
        ...
    ValueError: Missing from "params" dictionary in "complex_function": code
    """
    def __init__(self, required):
        self.required = set(required)

    def __call__(self, func):
        def wrapper(*args, **kwargs):
            if not kwargs.get('params', None):
                raise KeyError('"params" kwarg required for {0}'.format(func.__name__))
            missing = self.required.difference(kwargs['params'])
            if missing:
                raise ValueError('Missing from "params" dictionary in "{0}": {1}'.format(func.__name__, ', '.join(sorted(missing))))
            return func(*args, **kwargs)
        return wrapper

if __name__ == "__main__":
    import doctest
    doctest.testmod()

Answer 1

def wrapper(params): 意味着您只会接受一个参数——因此当然调用 (self, params) 是不会的工作。您需要能够接受一个或两个参数，例如，至少(如果您不需要支持带有命名参数的调用):

def wrapper(one, two=None):
  if two is None: params = one
  else: params = two
  # and the rest as above

为了也接受命名参数，您可以变得更加复杂/复杂，但这要简单得多并且仍然“大部分有效”；-)。