Python使用修饰器执行函数的参数检查功能示例

import html
def make_tagged(text, tag):
  return '<{0}>{1}</{0}>'.format(tag, html.escape(text))

def repeat(what, count, separator) :
  return ((what + separator)*count)[:-len(separator)]

import functools
def statically_typed(*types, return_type=None):
  def decorator(func):
    @functools.wraps(func)
    def wrapper(*args, **kwargs):
      if len(args) > len(types):
        raise ValueError('too many arguments')
      elif len(args) < len(types):
        raise ValueError('too few arguments')
      for i, (type_, arg) in enumerate(zip(types, args)):
        if not isinstance(type_, arg):
          raise ValueError('argument {} must be of type {}'.format(i, type_.__name__))
      result = func(*args, **kwargs)
      if return_type is not None and not isinstance(result, return_type):
        raise ValueError('return value must be of type {}'.format(return_type.__name__))
      return wrapper
    return decorator

@statically_typed(str, str, return_type=str)
def make_tagged(text, tag):
  return '<{0}>{1}</{0}>'.format(tag, html.escape(text))
@statically_typed(str, int, str)
def repeat(what, count, separator):
  return ((what + separator)*count)[:-len(separator)]