覆盖使用 from...import 的模块方法 [英] Override module method where from...import is used

问题描述

我无法覆盖使用 from...import 语句的方法.一些说明问题的例子:

I have problem to override method where from...import statement is used. Some example to illustrate the problem:

# a.py module
def print_message(msg):
    print(msg)

# b.py module
from a import print_message
def execute():
    print_message("Hello")

# c.py module which will be executed
import b
b.execute()

我想在不更改 a 或 b 模块中的代码的情况下覆盖 print_message(msg) 方法.我尝试了很多方法，但是 from...import 导入原始方法.当我将代码更改为

I'd like to override print_message(msg) method without changing code in a or b module. I tried in many ways but from...import imports original method. When I changed code to

import a
a.print_message

比我看到我的变化.

你能建议我如何解决这个问题吗?
在此先感谢您提供的任何小示例.

Could you suggest my how to solve this problem?
Thanks in advance for any little example.

最好的问候

------------------- 更新-------------------
我试着像下面那样做，例如:

------------------ Update ------------------
I tried to do that like below e.g.:

# c.py module
import b
import a
import sys
def new_print_message(msg):
    print("New content")
module = sys.modules["a"]
module.print_message = new_print_message
sys.module["a"] = module

但这在我使用 for...import 语句的地方不起作用.仅适用于导入 a，但正如我所写，我不想更改 b.py 和 a.py 模块中的代码.

But this is not working where I'm using for...import statement. Is working only for import a but as I wrote I don't want change code in b.py and a.py modules.

推荐答案

保持 a 和 b 模块不变，你可以尝试实现 c如下:

With your a and b modules untouched you could try implementing c as follows:

import a

def _new_print_message(message):
    print "NEW:", message

a.print_message = _new_print_message

import b
b.execute()

您必须首先导入 a，然后覆盖该函数，然后导入 b 以便它使用已经存在的 a 模块导入(并更改).

You have to first import a, then override the function and then import b so that it would use the a module that is already imported (and changed).

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