取消註冊singledispatch？

Question

有沒有辦法「註銷」一個通用的註冊函數？

例如：

from functools import singledispatch 

@singledispatch 
def foo(x): 
    return 'default function' 

foo.register(int, lambda x: 'function for int') 

# later I would like to revert this. 

foo.unregister(int) # does not exist - this is the functionality I am after 

Answer 1

singledispatch意味着是追加僅;你不能真正註銷任何東西。

但是與Python的所有東西一樣，的執行可能會被強制取消註冊。下面的函數會unregister()方法添加到singledispatch功能：

def add_unregister(func): 
    # build a dictionary mapping names to closure cells 
    closure = dict(zip(func.register.__code__.co_freevars, 
         func.register.__closure__)) 
    registry = closure['registry'].cell_contents 
    dispatch_cache = closure['dispatch_cache'].cell_contents 
    def unregister(cls): 
     del registry[cls] 
     dispatch_cache.clear() 
    func.unregister = unregister 
    return func 

這伸進singledispatch.register()功能關閉訪問實際registry字典，所以我們可以刪除已註冊現有的類。我也很清楚了dispatch_cache弱引用字典，以防止其在加強

您可以使用此作爲裝飾。

@add_unregister 
@singledispatch 
def foo(x): 
    return 'default function' 

演示：

>>> @add_unregister 
... @singledispatch 
... def foo(x): 
...  return 'default function' 
... 
>>> foo.register(int, lambda x: 'function for int') 
<function <lambda> at 0x10bed6400> 
>>> foo.registry 
mappingproxy({<class 'object'>: <function foo at 0x10bed6510>, <class 'int'>: <function <lambda> at 0x10bed6400>}) 
>>> foo(1) 
'function for int' 
>>> foo.unregister(int) 
>>> foo.registry 
mappingproxy({<class 'object'>: <function foo at 0x10bed6510>}) 
>>> foo(1) 
'default function'