Python 模块的动态加载

Dynamic Loading of Python Modules

提问by Ian

I'm trying to dynamically load modules I've created.

我正在尝试动态加载我创建的模块。

Right now this works properly:

现在这可以正常工作：

import structures.index

But if I try the same thing by importing it dynamically, it fails.

但是如果我通过动态导入来尝试同样的事情，它会失败。

struct = __import__("structures.index")

Error supplied is:

提供的错误是：

Error ('No module named structures.index',)

Any ideas why?

任何想法为什么？

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Edit: When using full scope (it sort of works?):

编辑：使用全范围时（它有点工作？）：

struct = __import__("neoform.structures.index")

This doesn't throw any errors, however, it isn't loading the index module, it's loading the "neoform" module instead.

这不会引发任何错误，但是，它不是加载索引模块，而是加载“neoform”模块。

The result of "struct" is:

“结构”的结果是：

<module 'neoform' from '/neoform/__init__.py'>

Also, as a side question, how can I then instantiate a class within a dynamically loaded module? (assuming all the modules contain a common class name).

另外，作为一个附带问题，我怎样才能在动态加载的模块中实例化一个类？（假设所有模块都包含一个公共类名）。

Edit: Solution: (thanks coonj & Rick) This ended up being what worked. Not sure why (yet), but the fromlisthad to be something "anything apparently, since it worked when I put the letter "a" as a value (strange, given that the file only had 1 class in it).

编辑：解决方案：（感谢 coonj 和 Rick）这最终奏效了。不知道为什么（还），但是fromlist必须是“任何显然的东西，因为当我将字母“a”作为值时它起作用（奇怪，因为文件中只有 1 个类）。

def get_struct_module(self, name):
    try:
        return = __import__("neoform.structures." + name, fromlist='*')
    except ImportError, e:
        self.out.add("Could not load struct: neoform.structure." + name + "\n\n" + "Error " + str(e.args))

回答by Rick Copeland

I'm not sure what "it fails" means, so I'll just mention that __import__('structures.index')should, in fact, work, but it doesn't assign the module name in the current scope. To do that (and then use a class in the dynamically imported module), you'll have to use:

我不确定“它失败”是什么意思，所以我只是提到它__import__('structures.index')实际上应该可以工作，但它不会在当前范围内分配模块名称。为此（然后在动态导入的模块中使用一个类），您必须使用：

structures = __import__('structures.index')
structures.index.SomeClass(...)

The complete details on __import__are available here.

的完整详细信息__import__可在此处获得。

Edit: (based on question edit)

编辑：（基于问题编辑）

To import neoform.structures.index, and return the indexmodule, you would do the following:

要导入neoform.structures.index并返回index模块，您将执行以下操作：

structures = __import__('neoform.structures.index', 
                        fromlist=['does not in fact matter what goes here!'])

So if you have a list of package names packages, you can import their indexmodules and instantiate some MyClassclass for each using the following code:

因此，如果您有一个包名称列表packages，您可以导入它们的index模块并MyClass使用以下代码为每个模块实例化一些类：

modules = [ __import__('neoform.%s.index' % pkg, fromlist=['a']) 
            for pkg in packages ]
objects = [ m.MyClass() for m in modules ]

回答by Jason Coon

To import sub-modules, you need to specify them in the fromlistarg of __import__()
Fo example, the equivalent of:

要导入子模块，需要在Fo 示例的fromlistarg 中指定它们__import__()
，相当于：

import structures.index

is:

是：

structures = __import__('structures', fromlist=['index'])

To do this in a map is a little more tricky...

在地图中做到这一点有点棘手......

import mod1.index
import mod2.index
import mod3.index

For those imports, you would want to define a new function to get the indexsub-module from each module:

对于这些导入，您需要定义一个新函数来index从每个模块中获取子模块：

def getIndexMods(mod_names):
  mod_list = map(lambda x: __import__(x, fromlist='index'))
  index_mods = [mod.index for mod in mod_list]
  return index_mods

Now, you can do this to get references to all index modules:

现在，您可以这样做以获取对所有索引模块的引用：

index_mods = getIndexMods(['mod1', 'mod2', 'mod3'])

Also, if you want to grab sub-modules that are not named 'index' then you could do this:

此外，如果您想获取未命名为“index”的子模块，则可以执行以下操作：

mod1, mod2, mod3 = map(lambda x,y: __import__(x, fromlist=y), 
  ['mod1', 'mod2', 'mod3'], ['index1', 'index2', 'index3'])

回答by FogleBird

Use full scope ("neoform.structures.index") with this helper method.

使用此辅助方法的完整范围（“neoform.structures.index”）。

def import_module(name):
    mod = __import__(name)
    components = name.split('.')
    for comp in components[1:]:
        mod = getattr(mod, comp)
    return mod

module = import_module("neoform.structures.index")
# do stuff with module

回答by rorycl

>>> import imp
>>> fm = imp.find_module('index', ['./structures']) # for submodule
>>> mymod = imp.load_module('structures.index', *fm)
>>> mymod
<module 'structures.index' from './structures/index.pyc'>
>>> x = mymod.insideIndex()
Initialising index class...

Voila!

瞧！

回答by dfa

Java programmer here, but I think you need the imp module

Java程序员在这里，但我认为你需要imp模块

回答by S.Lott

Why on earth would you replace

你到底为什么要更换

import structures.index

with

和

map(__import__, ["structures.index"])

The first one (a) works, (b) isdynamic and (c) is directly supported. What possible use case is there for replacing easy-to-change, plain-text source with something more complex?

第一个 (a) 有效，(b)是动态的，(c) 是直接支持的。有什么可能的用例可以用更复杂的东西替换易于更改的纯文本源？

In short: don't do this. It doesn't have any value.

简而言之：不要这样做。它没有任何价值。

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Edit

编辑

The "I'm getting the import from a database" is a noble effort, but still not sensible. What code block depends on those imports? That whole code block -- imports and all -- is what you want to execute. That whole code block -- imports, statements and everything -- should be a plain old python module file.

“我正在从数据库获取导入”是一项崇高的努力，但仍然不明智。哪些代码块取决于这些导入？整个代码块——导入和所有——就是你想要执行的。整个代码块——导入、语句和一切——应该是一个普通的旧 python 模块文件。

Import that block of code from the file system. Use the database to identify which file, the author of the file -- anything you want to use the database for. But simply import and execute the module the simplest possible way.

从文件系统导入该代码块。使用数据库来识别哪个文件，文件的作者——任何你想使用数据库的东西。但只需以最简单的方式导入和执行模块。

回答by jdsantiagojr

Really late post here. But I was searching for this question on google. I did some trial and error. Not sure if this snippet will help but here it is. Using it for Flask site.

在这里发帖真的晚了。但是我在谷歌上搜索这个问题。我做了一些试验和错误。不确定这个片段是否会有所帮助，但它在这里。将其用于 Flask 站点。

modules = ['frontend', 'admin']
for module in modules:
    mod = __init__('controllers.%s' % module, fromlist=[module])
    app.register_blueprint(mod.blueprint_mod)


# or
from importlib import import_module
modules = ['frontend', 'admin']
for module in modules:
    mod = import_module('controllers.%s' % module)
    app.regitster_blueprint(mod.blueprint_mod)