你可以使用importlib.reload()重新加载一个已经被导入的模块:

from importlib import reload  # Python 3.4+
import foo

while True:
    # Do some things.
    if is_changed(foo):
        foo = reload(foo)

在Python 2中，重载是内置的。在Python 3中，它被移动到imp模块。在3.4中，弃用了imp，改用了importlib。当目标为3或更高版本时，在调用reload或import时引用适当的模块。

我觉得这就是你想要的。像Django的开发服务器这样的Web服务器使用了这个功能，这样你就可以在不重启服务器进程的情况下看到代码更改的效果。

引用文件中的内容:

Python module’s code is recompiled and the module-level code re-executed, defining a new set of objects which are bound to names in the module’s dictionary by reusing the loader which originally loaded the module. The init function of extension modules is not called a second time. As with all other objects in Python the old objects are only reclaimed after their reference counts drop to zero. The names in the module namespace are updated to point to any new or changed objects. Other references to the old objects (such as names external to the module) are not rebound to refer to the new objects and must be updated in each namespace where they occur if that is desired.

正如您在问题中所指出的，如果Foo类驻留在Foo模块中，则必须重新构造Foo对象。

其他选项。请参阅Python默认importlib。Reload将只是重新导入作为参数传递的库。它不会重新加载库导入的库。如果您更改了很多文件，并且有一个有点复杂的包要导入，那么您必须进行深度重载。

如果你安装了IPython或Jupyter，你可以使用一个函数来深度重载所有库:

from IPython.lib.deepreload import reload as dreload
dreload(foo)

如果你没有Jupyter，在你的shell中使用以下命令安装它:

pip3 install jupyter

编辑(答案V2)

前面的解决方案只适用于获取重置信息，但它不会更改所有引用(超过重新加载，但小于所需)。为了设置所有的引用，我必须进入垃圾收集器，并在那里重写引用。现在它就像一个咒语!

请注意，如果GC被关闭，或者如果重新加载不受GC监视的数据，这将不起作用。如果您不想打乱GC，原始答案可能就足够了。

新代码:

import importlib
import inspect
import gc
from enum import EnumMeta
from weakref import ref


_readonly_attrs = {'__annotations__', '__call__', '__class__', '__closure__', '__code__', '__defaults__', '__delattr__',
               '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__func__', '__ge__', '__get__',
               '__getattribute__', '__globals__', '__gt__', '__hash__', '__init__', '__init_subclass__',
               '__kwdefaults__', '__le__', '__lt__', '__module__', '__name__', '__ne__', '__new__', '__qualname__',
               '__reduce__', '__reduce_ex__', '__repr__', '__self__', '__setattr__', '__sizeof__', '__str__',
               '__subclasshook__', '__weakref__', '__members__', '__mro__', '__itemsize__', '__isabstractmethod__',
               '__basicsize__', '__base__'}


def reset_module(module, inner_modules_also=True):
    """
    This function is a stronger form of importlib's `reload` function. What it does, is that aside from reloading a
    module, it goes to the old instance of the module, and sets all the (not read-only) attributes, functions and classes
    to be the reloaded-module's
    :param module: The module to reload (module reference, not the name)
    :param inner_modules_also: Whether to treat ths module as a package as well, and reload all the modules within it.
    """

    # For the case when the module is actually a package
    if inner_modules_also:
        submods = {submod for _, submod in inspect.getmembers(module)
                   if (type(submod).__name__ == 'module') and (submod.__package__.startswith(module.__name__))}
        for submod in submods:
            reset_module(submod, True)

    # First, log all the references before reloading (because some references may be changed by the reload operation).
    module_tree = _get_tree_references_to_reset_recursively(module, module.__name__)

    new_module = importlib.reload(module)
    _reset_item_recursively(module, module_tree, new_module)


def _update_referrers(item, new_item):
    refs = gc.get_referrers(item)

    weak_ref_item = ref(item)
    for coll in refs:
        if type(coll) == dict:
            enumerator = coll.keys()
        elif type(coll) == list:
            enumerator = range(len(coll))
        else:
            continue

        for key in enumerator:

            if weak_ref_item() is None:
                # No refs are left in the GC
                return

            if coll[key] is weak_ref_item():
                coll[key] = new_item

def _get_tree_references_to_reset_recursively(item, module_name, grayed_out_item_ids = None):
    if grayed_out_item_ids is None:
        grayed_out_item_ids = set()

    item_tree = dict()
    attr_names = set(dir(item)) - _readonly_attrs
    for sub_item_name in attr_names:

        sub_item = getattr(item, sub_item_name)
        item_tree[sub_item_name] = [sub_item, None]

        try:
            # Will work for classes and functions defined in that module.
            mod_name = sub_item.__module__
        except AttributeError:
            mod_name = None

        # If this item was defined within this module, deep-reset
        if (mod_name is None) or (mod_name != module_name) or (id(sub_item) in grayed_out_item_ids) \
                or isinstance(sub_item, EnumMeta):
            continue

        grayed_out_item_ids.add(id(sub_item))
        item_tree[sub_item_name][1] = \
            _get_tree_references_to_reset_recursively(sub_item, module_name, grayed_out_item_ids)

    return item_tree


def _reset_item_recursively(item, item_subtree, new_item):

    # Set children first so we don't lose the current references.
    if item_subtree is not None:
        for sub_item_name, (sub_item, sub_item_tree) in item_subtree.items():

            try:
                new_sub_item = getattr(new_item, sub_item_name)
            except AttributeError:
                # The item doesn't exist in the reloaded module. Ignore.
                continue

            try:
                # Set the item
                _reset_item_recursively(sub_item, sub_item_tree, new_sub_item)
            except Exception as ex:
                pass

    _update_referrers(item, new_item)

原来的答案

正如在@bobince的回答中所写的，如果在另一个模块中已经有对该模块的引用(特别是如果它是用As关键字导入的，如import numpy As np)，该实例将不会被覆盖。

当应用需要配置模块的“全新”状态的测试时，这对我来说是相当有问题的，所以我写了一个名为reset_module的函数，它使用importlib的reload函数并递归地覆盖所有声明的模块属性。它已经用Python版本3.6进行了测试。

import importlib
import inspect
from enum import EnumMeta

_readonly_attrs = {'__annotations__', '__call__', '__class__', '__closure__', '__code__', '__defaults__', '__delattr__',
               '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__func__', '__ge__', '__get__',
               '__getattribute__', '__globals__', '__gt__', '__hash__', '__init__', '__init_subclass__',
               '__kwdefaults__', '__le__', '__lt__', '__module__', '__name__', '__ne__', '__new__', '__qualname__',
               '__reduce__', '__reduce_ex__', '__repr__', '__self__', '__setattr__', '__sizeof__', '__str__',
               '__subclasshook__', '__weakref__', '__members__', '__mro__', '__itemsize__', '__isabstractmethod__',
               '__basicsize__', '__base__'}


def reset_module(module, inner_modules_also=True):
    """
    This function is a stronger form of importlib's `reload` function. What it does, is that aside from reloading a
    module, it goes to the old instance of the module, and sets all the (not read-only) attributes, functions and classes
    to be the reloaded-module's
    :param module: The module to reload (module reference, not the name)
    :param inner_modules_also: Whether to treat ths module as a package as well, and reload all the modules within it.
    """

    new_module = importlib.reload(module)

    reset_items = set()

    # For the case when the module is actually a package
    if inner_modules_also:
        submods = {submod for _, submod in inspect.getmembers(module)
                   if (type(submod).__name__ == 'module') and (submod.__package__.startswith(module.__name__))}
        for submod in submods:
            reset_module(submod, True)

    _reset_item_recursively(module, new_module, module.__name__, reset_items)


def _reset_item_recursively(item, new_item, module_name, reset_items=None):
    if reset_items is None:
        reset_items = set()

    attr_names = set(dir(item)) - _readonly_attrs

    for sitem_name in attr_names:

        sitem = getattr(item, sitem_name)
        new_sitem = getattr(new_item, sitem_name)

        try:
            # Set the item
            setattr(item, sitem_name, new_sitem)

            try:
                # Will work for classes and functions defined in that module.
                mod_name = sitem.__module__
            except AttributeError:
                mod_name = None

            # If this item was defined within this module, deep-reset
            if (mod_name is None) or (mod_name != module_name) or (id(sitem) in reset_items) \
                    or isinstance(sitem, EnumMeta):  # Deal with enums
                continue

            reset_items.add(id(sitem))
            _reset_item_recursively(sitem, new_sitem, module_name, reset_items)
        except Exception as ex:
            raise Exception(sitem_name) from ex

注意事项:请谨慎使用!在非外围模块(例如，定义外部使用的类的模块)上使用这些可能会导致Python中的内部问题(例如pickle / unpickling问题)。

对于像我这样想卸载所有模块的人(当在Emacs下的Python解释器中运行时):

   for mod in sys.modules.values():
      reload(mod)

更多信息请参见重新加载Python模块。

如果一个模块不是纯Python的，那么删除它会特别困难。

下面是来自:如何真正删除导入的模块?

您可以使用sys.getrefcount()来找出的实际数量 参考文献

>>> import sys, empty, os
>>> sys.getrefcount(sys)
9
>>> sys.getrefcount(os)
6
>>> sys.getrefcount(empty)
3

大于3的数字表示 它将很难摆脱 模块。本土的“空” (不包含任何内容)模块应该 垃圾收集后

>>> del sys.modules["empty"]
>>> del empty

因为第三个参考是一个人工制品 getrefcount()函数的。

接受的答案不处理from X import Y的情况。这段代码处理了它和标准的导入情况:

def importOrReload(module_name, *names):
    import sys

    if module_name in sys.modules:
        reload(sys.modules[module_name])
    else:
        __import__(module_name, fromlist=names)

    for name in names:
        globals()[name] = getattr(sys.modules[module_name], name)

# use instead of: from dfly_parser import parseMessages
importOrReload("dfly_parser", "parseMessages")

在重新加载的情况下，我们将顶级名称重新分配给新加载的模块中存储的值，从而更新这些值。