[英]Programmatically changing docstring of a class object
I have a function and class decorator that changes them to singletons but the docstrings are kind of dropped. 我有一个函数和类装饰器,将它们更改为单例,但文档字符串有点丢弃。 Transforming function returns a class object that has its own docstring which should be overwritten.
转换函数返回一个具有自己的docstring的类对象,该对象应该被覆盖。 How can I work around this?
我该如何解决这个问题?
def singleton(cls):
return cls()
def singletonfunction(func):
return func()
@singletonfunction
def Bit():
"""A 1-bit BitField; must be enclosed in a BitStruct"""
return BitsInteger(1)
Inspecting Bit
yields the BitInteger
docstring, not the function's one. 检查
Bit
产生BitInteger
文档字符串,而不是函数的字符串。
Lets assume the original version is something like this: 让我们假设原始版本是这样的:
class BitsInteger:
"""BitsInteger docstring"""
def __init__(self, num):
pass
def singleton(cls):
return cls()
def singletonfunction(func):
return func()
@singletonfunction
def Bit():
"""A 1-bit BitField; must be enclosed in a BitStruct"""
return BitsInteger(1)
b = Bit
print("b.__doc__ :", b.__doc__)
Running this with Python3.5 gives the output: 使用Python3.5运行它会得到输出:
b.__doc_ : BitsInteger docstring
This might not be what you expect. 这可能不是您所期望的。 When we run with
python -i original.py
we can have a look around at what is really going on here: 当我们使用
python -i original.py
运行时,我们可以看看这里真正发生的事情:
>>> vars()
{'__name__': '__main__', '__builtins__': <module 'builtins' (built-in)>, 'b': <__main__.BitsInteger object at 0x7ff05d2ae3c8>, '__spec__': None, 'singletonfunction': <function singletonfunction at 0x7ff05d2b40d0>, 'singleton': <function singleton at 0x7ff05d30cd08>, '__cached__': None, 'BitsInteger': <class '__main__.BitsInteger'>, '__loader__': <_frozen_importlib.SourceFileLoader object at 0x7ff05d2eb4a8>, '__package__': None, 'Bit': <__main__.BitsInteger object at 0x7ff05d2ae3c8>, '__doc__': None}
>>>
As you can see b
is actually of type BitsInteger
如您所见,
b
实际上是BitsInteger
类型
The reason is because what's really going on is that when you write: 原因是因为当你写作时,真正发生的是:
@singleton_function
def Bit():
"""Bit docstring"""
...
return BitsInteger(1)
You are really just getting syntactic sugar for this: 你真的只是为此获得语法糖:
def Bit():
"""Bit docstring"""
...
return BitsInteger(1)
Bit = singleton_function(Bit)
In this case Bit
is the return value of singleton_function
which is actually a BitsInteger
. 在这种情况下,
Bit
是singleton_function
的返回值,它实际上是一个BitsInteger
。 I find when you strip back the syntactic sugar it's much clearer what's going on here. 我发现当你剥离语法糖时,它会更清楚这里发生了什么。
If you would like to have the convenience of a decorator that doesn't change the docstring I'd recommend using wrapt 如果你想拥有一个不会改变docstring的装饰器的便利,我建议使用wrapt
import wrapt
class BitsInteger:
"""BitsInteger docstring"""
def __init__(self, num):
pass
def singleton(cls):
return cls()
@wrapt.decorator
def singletonfunction(func):
return func()
@singletonfunction
def Bit():
"""A 1-bit BitField; must be enclosed in a BitStruct"""
return BitsInteger(1)
b = Bit
print("b.__doc_ :", b.__doc__)
This outputs: 这输出:
b.__doc_ : A 1-bit BitField; must be enclosed in a BitStruct
Now when you look at Vars()
you see that 'b': <FunctionWrapper at 0x7f9a9ac42ba8 for function at 0x7f9a9a9e8c80>
which is no longer a BitInteger
type. 现在,当你看到
Vars()
你会看到'b': <FunctionWrapper at 0x7f9a9ac42ba8 for function at 0x7f9a9a9e8c80>
它不再是BitInteger
类型。 Personally I like using wrapt because I get what I want immediately. 我个人喜欢使用包装,因为我得到了我想要的东西。 Implementing that functionality and covering all the edge cases takes effort and I know that wrapt is well tested and works as intended.
实现该功能并涵盖所有边缘情况需要付出努力,我知道包装已经过充分测试并且按预期工作。
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