在交互式上删除了模块的功能。如何重新导入？ importlib.reload没有帮助 [英] Deleted a module's function on interactive. How to re-import? importlib.reload not helping

问题描述

我在ipython上删除了（package builtin）函数：

I've deleted a (package builtin) function on ipython:

Python 3.6.4 |Anaconda custom (64-bit)| (default, Jan 16 2018, 10:22:32) [MSC v.1900 64 bit (AMD64)]
Type 'copyright', 'credits' or 'license' for more information
IPython 6.2.1 -- An enhanced Interactive Python. Type '?' for help.

In [1]: import math

In [2]: math.cos(0)
Out[2]: 1.0

In [3]: del math.cos

In [4]: math.cos(0)
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-4-9cdcc157d079> in <module>()
----> 1 math.cos(0)

AttributeError: module 'math' has no attribute 'cos'

好的。但是如何重新加载该功能？这没有帮助：

OK. But how do I reload the function? This didn't help:

In [5]: import importlib

In [6]: importlib.reload(math)
Out[6]: <module 'math' (built-in)>

In [7]: math.cos(0)
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-7-9cdcc157d079> in <module>()
----> 1 math.cos(0)

AttributeError: module 'math' has no attribute 'cos'

推荐答案

上面的代码适用于Windows上的Python 3.4，但文档：

The above code works for me in Python 3.4 on Windows but the documentation for 3.6 states:

请注意，好像你保留了对模块对象，使其在sys.modules中的缓存条目无效，然后重新导入命名模块，这两个模块对象将不相同。相比之下，importlib.reload（）将重用相同的模块对象，只需重新运行模块的代码即可重新初始化模块内容。

Beware though, as if you keep a reference to the module object, invalidate its cache entry in sys.modules, and then re-import the named module, the two module objects will not be the same. By contrast, importlib.reload() will reuse the same module object, and simply reinitialise the module contents by rerunning the module’s code.

（所以也许我只是幸运）

(so maybe I was only "lucky")

所以可以肯定的是：

import math,sys
del math.cos
del math
sys.modules.pop("math")   # remove from loaded modules
import math
print(math.cos(0))

它仍然有效，你不要甚至需要重新加载。只需从缓存中移除&再次导入。

It still works, and you don't even need reload. Just remove from cache & import again.

如评论中所述，使用 reload 也可以，但是你需要更新给定的模块参考通过重新加载，而不仅仅重复使用缺少 cos 条目的旧版本：

As noted in comments, using reload also works, but you need to update the module reference given by reload, not just reuse the same old one with the cos entry missing:

import math,sys
del math.cos
import importlib
math = importlib.reload(math)
print(math.cos(0))

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