Python 反射含有协程方法类的问题

a = __import__('a') print('===========getattr()=============') func_sync = getattr(a, 'func_sync') func_async = getattr(a, 'func_async') print(func_sync) # <function func_sync at 0x7f827b98f510> print(func_async) # <function func_async at 0x7f8279cd01e0> print(asyncio.iscoroutinefunction(func_async)) # True # getattr class A = getattr(a, 'A') print(A) # <class 'a.A'> method_aa = getattr(A, 'aa') method_bb = getattr(A, 'bb') method_cc = getattr(A, 'cc') print(method_aa) # <bound method A.aa of <class 'a.A'>> <----这里的 bound method 是什么意思？ print(method_bb) # <function A.bb at 0x7f8279cd00d0> print(method_cc) # <function A.cc at 0x7f8279cd0158> print(asyncio.iscoroutinefunction(method_aa)) # True <---- 注意这里 print(asyncio.iscoroutinefunction(method_bb)) # True print(asyncio.iscoroutinefunction(method_cc)) # False

使用__dict__

print('=========== __dict__ =============') A = a.__dict__['A'] func_sync = a.__dict__['func_sync'] func_async = a.__dict__['func_async'] print(asyncio.iscoroutinefunction(func_async)) # True print(A) # <class 'a.A'> method_aa = A.__dict__['aa'] method_bb = A.__dict__['bb'] method_cc = A.__dict__['cc'] print(method_aa) # <classmethod object at 0x7f827a21c908> <---- 变成了 classmethod print(method_bb) # <function A.bb at 0x7f8279cd00d0> print(method_cc) # <function A.cc at 0x7f8279cd0158> print(asyncio.iscoroutinefunction(method_aa)) # False <----- 不应该是 True 吗？ print(asyncio.iscoroutinefunction(method_bb)) # True print(asyncio.iscoroutinefunction(method_cc)) # False

我感觉__dict__和getattr()在反射对象的机制上应该有一些区别，但是 google 了半天也没搞明白为什么，求指教！

a.py

class A: @classmethod async def aa(cls): return 123 async def bb(self): return 456 def cc(self): return 789 def func_sync(): return 'sync' async def func_async(): return 'async'

getattr

dict__

rou

7 条回复 2018-06-19 10:26:51 +08:00

wwqgtxx

2018-06-18 13:20:41 +08:00

个人猜测，应该原因在这里：

asyncio.iscoroutinefunction:
return (getattr(func, '_is_coroutine', None) is _is_coroutine or _inspect_iscoroutinefunction(func))

inspect.iscoroutinefunction:
return bool((isfunction(object) or ismethod(object)) andobject.__code__.co_flags & CO_COROUTINE)

通过实验
>>>A.aa
<bound method A.aa of <class 'A'>>
>>>A.__dict__["aa"]
<classmethod object at 0x000002BDE92F7F60>
>>>inspect.ismethod(A.__dict__["aa"])
False
>>>inspect.isfunction(A.__dict__["aa"])
False
>>>inspect.ismethod(A.aa)
True
>>>inspect.isfunction(A.aa)
False

所以你通过 A.__dict__['a']得到的是一个 classmethod object 而根本就不是一个 method 也不是一个 function，当然他也就不是一个 coroutinefunction 了，至于为什么这么判断，那就得看写这段代码的人是怎么想的了