如何覆盖Python导入？ [英] How do I override a Python import?
问题描述
我正在开发 pypreprocessor ，这是一个采用c风格指令的预处理器我已经能够使它像传统的预处理器一样工作（它是自耗的并且即时执行后处理代码），除了它打破了库的导入。
I'm working on pypreprocessor which is a preprocessor that takes c-style directives and I've been able to make it work like a traditional preprocessor (it's self-consuming and executes postprocessed code on-the-fly) except that it breaks library imports.
问题是：预处理器运行文件，处理它，输出到临时文件，exec（）临时文件。导入的库需要处理稍微不同，因为它们不会被执行，而是被加载并且可以被调用者模块访问。
The problem is: The preprocessor runs through the file, processes it, outputs to a temporary file, and exec() the temporary file. Libraries that are imported need to be handled a little different, because they aren't executed, but rather they are loaded and made accessible to the caller module.
我需要什么能够做的是：中断导入（因为预处理器正在导入的中间运行），将后处理的代码作为tempModule加载，并将原始导入替换为tempModule，以通过导入来欺骗调用脚本相信tempModule是原始模块。
What I need to be able to do is: Interrupt the import (since the preprocessor is being run in the middle of the import), load the postprocessed code as a tempModule, and replace the original import with the tempModule to trick the calling script with the import into believing that the tempModule is the original module.
到目前为止，我已到处搜索并且没有解决方案。
I have searched everywhere and so far and have no solution.
这个Stack Overflow问题是我到目前为止提供答案的最接近的问题：
Override Python中的命名空间
This Stack Overflow question is the closest I've seen so far to providing an answer: Override namespace in Python
这就是我所拥有的。
# Remove the bytecode file created by the first import
os.remove(moduleName + '.pyc')
# Remove the first import
del sys.modules[moduleName]
# Import the postprocessed module
tmpModule = __import__(tmpModuleName)
# Set first module's reference to point to the preprocessed module
sys.modules[moduleName] = tmpModule
moduleName是名称原始模块的名称，tmpModuleName是后处理代码文件的名称。
moduleName is the name of the original module, and tmpModuleName is the name of the postprocessed code file.
奇怪的是，这个解决方案仍然完全正常运行，就像第一个模块完成正常加载一样;除非你删除最后一行，否则你会得到一个模块未找到错误。
The strange part is this solution still runs completely normal as if the first module completed loaded normally; unless you remove the last line, then you get a module not found error.
希望Stack Overflow上的某些人比我更了解进口，因为这个让我难过。
Hopefully someone on Stack Overflow know a lot more about imports than I do, because this one has me stumped.
注意：我只会奖励一个解决方案，或者，如果在Python中无法做到这一点;最好，最详细的解释为什么这不是不可能的。
更新：对于任何感兴趣的人，这是工作代码。
if imp.lock_held() is True:
del sys.modules[moduleName]
sys.modules[tmpModuleName] = __import__(tmpModuleName)
sys.modules[moduleName] = __import__(tmpModuleName)
'imp.lock_held'部分检测模块是否作为库加载。以下几行完成其余的工作。
The 'imp.lock_held' part detects whether the module is being loaded as a library. The following lines do the rest.
推荐答案
这是否回答了你的问题？第二个导入就是这个诀窍。
Does this answer your question? The second import does the trick.
Mod_1.py
def test_function():
print "Test Function -- Mod 1"
Mod_2.py
def test_function():
print "Test Function -- Mod 2"
Test.py
#!/usr/bin/python
import sys
import Mod_1
Mod_1.test_function()
del sys.modules['Mod_1']
sys.modules['Mod_1'] = __import__('Mod_2')
import Mod_1
Mod_1.test_function()
这篇关于如何覆盖Python导入？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
