删除了模块的交互功能。如何重新导入？ importlib.reload 没有帮助

Question

我删除了 ipython 上的一个（程序包内置）函数：

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：

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'

Answer 1

上面的代码在 Python 3.4 on Windows 中对我有用，但是 documentation for 3.6 states:

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.

（所以也许我只有 "lucky"）

所以肯定有效的是：

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，您甚至不需要 reload。只需从缓存中删除并再次导入。

如评论中所述，使用 reload 也可以，但您需要更新 reload 给出的模块引用，而不是仅仅重复使用带有 cos 条目的旧模块引用缺少：

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

Answer 2

好的，我写了一个小模块来解决这个困惑。我真诚地怀疑它是没有错误的。所以欢迎改进。

这个模块在 Py 2 和 3 上都运行良好。在 Python 2.7 和 Python 3.5 上试过。



# rld.py --> the reloading module

import sys

__all__ = ["reload"]

try:
    # Python 2:
    _reload = reload
    from thread import get_ident
    def reload (module):
        if isinstance(module, basestring):
            module = sys.modules[module]
        if module.__name__==__name__:
            raise RuntimeError("Reloading the reloading module is not supported!")
        print ("Reloading: %s" % module.__name__)
        # Get locals() of a frame that called us:
        ls = sys._current_frames()[get_ident()].f_back.f_locals
        # Find variables holding the module:
        vars = [name for name, mod in ls.iteritems() if mod==module]
        if len(vars)==0:
            print ("Warning: Module '%s' has no references in this scope.\nReload will be attempted anyway." % module.__name__)
        else:
            print("Module is referenced as: %s" % repr(vars))
        # Reload:
        m = _reload(module)
        for x in vars:
            ls[x] = m
        print("Reloaded!")
except NameError:
    # Python 3:
    from _thread import get_ident
    def reload (module):
        if isinstance(module, str):
            module = sys.modules[module]
        if module.__name__==__name__:
            raise RuntimeError("Reloading the reloading module is not supported!")
        print ("Reloading: %s" % module.__name__)
        # Get locals() of a frame that called us:
        ls = sys._current_frames()[get_ident()].f_back.f_locals
        # Find variables holding the module:
        vars = [name for name, mod in ls.items() if mod==module]
        if len(vars)==0:
            print ("Warning: Module '%s' has no references in this scope.\nReload will be attempted anyway." % module.__name__)
        else:
            print("Module is referenced as: %s" % repr(vars))
        # Dereference all detected:
        for x in vars:
            del ls[x]
        del sys.modules[module.__name__]
        # Reimport:
        m = __import__(module.__name__)
        # Rebind to old variables:
        for x in vars:
            ls[x] = m
        # Remap references in the old module
        # to redirect all other modules that already imported that module:
        for vname in dir(m):
            setattr(module, vname, getattr(m, vname))
        print("Reloaded!")

>>> # Usage:
>>> from rld import * # Always import it first - just in case
>>> import math
>>> math.cos
<built-in function cos>
>>> del math.cos
>>> math.cos
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'module' object has no attribute 'cos'
>>> reload(math)
Reloading: math
Module is referenced as: ['math']
Reloaded!
>>> math.cos
<built-in function cos>
>>> #-------------------------
>>> # This also works:
>>> import math as quiqui
>>> alias = quiqui
>>> del quiqui.cos
>>> quiqui.cos
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'module' object has no attribute 'cos'
>>> alias.cos
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'module' object has no attribute 'cos'
>>> reload("math")
Reloading: math
Module is referenced as: ['alias', 'quiqui']
>>> quiqui.cos
<built-in function cos>
>>> alias.cos
<built-in function cos>

删除了模块的交互功能。如何重新导入？ importlib.reload 没有帮助

Deleted a module's function on interactive. How to re-import? importlib.reload not helping

python

python-3.x

ipython

python-importlib