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我正在编写一个处理程序来处理不同类型的数据。这是我目前的解决方案：

def get_handler_by_type(type):
    def handler_for_type_A:
        ...
        #code for processing data type A

    def handler_for_type_B:
        ...
        #code for processing data type B

    def handler_for_type_C:
        ...
        #code for processing data type C

    handler_map = {type_A: handler_for_type_A,
               type_B: handler_for_type_B,
               type_C: handler_for_type_C,
              }
    return handler_map(type)

但是，这似乎非常低效，因为我会经常调用 get_handler_by_type 并且每次调用它时，都会再次构造字典。

我知道我可以这样做：

def handler_for_type_A:
    ...
    #code for processing data type A

def handler_for_type_B:
    ...
    #code for processing data type B

def handler_for_type_C:
    ...
    #code for processing data type C

handler_map = {type_A: handler_for_type_A,
                type_B: handler_for_type_B,
                type_C: handler_for_type_C,
            }

def get_handler_by_type(type, handler_map = handler_map):
    return handler_map(type)

但在我看来，这很丑陋。因为我有 handler_for_type_Xs 和 handler_map 正在污染全局空间。有没有办法既高效又优雅地做到这一点？

感谢您的任何意见。

4

2 回答 2

2

一种方法是动态查找处理程序（如果您有一致的命名约定）

return vars()['handler_for_'+type]

另一种方法是将地图存储为函数的属性

def get_handler_by_type(type):
    def handler_for_type_A:
        ...
        #code for processing data type A

    def handler_for_type_B:
        ...
        #code for processing data type B

    def handler_for_type_C:
        ...
        #code for processing data type C

    if not hasattr(get_handler_by_type, 'handler_map'):
        get_handler_by_type.handler_map = {'type_A': handler_for_type_A,
               'type_B': handler_for_type_B,
               'type_C': handler_for_type_C,
              }

    return get_handler_by_type.handler_map[type]
于 2013-03-15T03:39:54.807 回答
1

这种方式将封装它：

def _handler_helper():
   def fna():
      print "a" 
      pass

   def fnb():
      print "b" 
      pass

   m = {"a":fna,"b":fnb}
   return lambda x:m[x]

get_handler_by_type = _handler_helper()

如果您想要一个文档字符串，您可能想要使用def，但这有效。

另一种选择可能是采用更多的 OOP 方法：

class _HandlerHelper:
   def fna(self):
       print 'a'

   def fnb(self):
       print 'b'

   # __call__ is a magic method which lets you treat the object as a function
   def __call__(self, fn):
       return getattr(self, 'fn' + fn)

get_handler_by_type = _HandlerHelper()
于 2013-03-15T03:36:57.263 回答