Python自然沒有型別強制轉換一說了，因為它是動態語言。首先，所有物件都從Object繼承而來，其次，它有強大的內省，如果呼叫某個不存在的方法會有異常丟擲。大多數情況，我們都不需要做引數型別栓查，除了一些特殊情況。例如，某個函式接受一個str型別，結果在實際呼叫時傳入的是unicode，測試過程中又沒有程式碼覆蓋到，這樣問題就比較嚴重了。解決方法也很簡單，藉助Python的內省，很容易就能判斷出引數的型別。但是每個地方都寫檢查程式碼會很累贅，何況它帶來的實際價值並不高。一個好的解決方法是使用裝飾器。

'''
  >>> NONE, MEDIUM, STRONG = 0, 1, 2
  >>>
  >>> @accepts(int, int, int)
  ... def average(x, y, z):
  ...     return (x + y + z) / 2
  ...
  >>> average(5.5, 10, 15.0)
  TypeWarning:  'average' method accepts (int, int, int), but was given
  (float, int, float)
  15.25
'''
def accepts(*types, **kw):
    """ Function decorator. Checks that inputs given to decorated function
    are of the expected type.

    Parameters:
    types -- The expected types of the inputs to the decorated function.
             Must specify type for each parameter.
    kw    -- Optional specification of 'debug' level (this is the only valid
             keyword argument, no other should be given).
             debug = ( 0 | 1 | 2 )

    """
    if not kw:
        # default level: MEDIUM
        debug = 1
    else:
        debug = kw['debug']
    try:
        def decorator(f):
            def newf(*args):
                if debug == 0:
                    return f(*args)
                assert len(args) == len(types)
                argtypes = tuple(map(type, args))
                if argtypes != types:
                    msg = info(f.__name__, types, argtypes, 0)
                    if debug == 1:
                        print >> sys.stderr, 'TypeWarning: ', msg
                    elif debug == 2:
                        raise TypeError, msg
                return f(*args)
            newf.__name__ = f.__name__
            return newf
        return decorator
    except KeyError, key:
        raise KeyError, key + "is not a valid keyword argument"
    except TypeError, msg:
        raise TypeError, msg

def info(fname, expected, actual, flag):
    """ Convenience function returns nicely formatted error/warning msg. """
    format = lambda types: ', '.join([str(t).split("'")[1] for t in types])
    expected, actual = format(expected), format(actual)
    msg = "'%s' method " % fname \
          + ("accepts", "returns")[flag] + " (%s), but " % expected\
          + ("was given", "result is")[flag] + " (%s)" % actual
    return msg