如何在没有 .py 文件的情况下导入 Python 模块(共享库)? [英] How are Python modules (which are shared libraries) imported without a .py file?

问题描述

我正在运行交互式 Python shell，并尝试使用inspect"模块查看导入模块的路径.我尝试导入的模块使用 SWIG 对 C++ API 进行了 Python 包装.

以下代码段显示了我的步骤:

<预><代码>>>>导入操作系统>>>进口检验>>>>>>导入数据库>>>检查.getfile(db)'mypath1/lib/db/db.pyc'>>>>>>进口飞镖>>>检查.getfile(飞镖)'mypath2/lib/dart.so'>>>

我的 PYTHONPATH 包含 mypath1/lib/db 和 mypath2/lib.

我的印象是，为了能够加载模块，解释器需要访问 .py 文件，然后调用 imp.load_module 来加载所需的共享库(.so 文件).这是我在 db 模块的情况下看到的，该模块在 mypath1/lib/db 下有一个 db.py 文件.但是，dart 在 mypath2/lib 下没有 .py 文件.

是否可以像 dart 模块那样导入没有 .py 文件的模块?

解决方案

Python 为任何给定的 import 搜索几个不同的文件，包括具有该名称的目录并包含 __init__.py，纯原生 Python 模块的 .so 文件和 .pyc 文件，即使删除了 .py 也可以使用.

运行 strace -o trace_output.txt python 以查看其工作原理.import md5 的部分示例:

stat("/usr/lib/python2.7/md5", 0x7fff81ff16d0) = -1 ENOENT (没有那个文件或目录)open("/usr/lib/python2.7/md5.x86_64-linux-gnu.so", O_RDONLY) = -1 ENOENT (没有那个文件或目录)open("/usr/lib/python2.7/md5.so", O_RDONLY) = -1 ENOENT (没有那个文件或目录)open("/usr/lib/python2.7/md5module.so", O_RDONLY) = -1 ENOENT(没有那个文件或目录)打开(/usr/lib/python2.7/md5.py"，O_RDONLY)= 3

在我的设置中，它实际上是在搜索:

• ~/.local/lib/python2.7/
• /usr/local/lib/python2.7/dist-packages
• /usr/lib/python2.7/dist-packages
• /usr/lib/python2.7/

在每个目录中，调用stat查找目录然后查找.so文件，然后.py的模式.

有关编写纯原生 Python 模块的更多信息，请参见此处:https://docs.python.org/2/extending/index.html

I am running an interactive Python shell and trying to see the path from which a module is being imported using the 'inspect' module. The modules I am trying to import have Python wrappers around C++ APIs using SWIG.

The following snippet shows my steps :

>>> import os
>>> import inspect
>>>      
>>> import db
>>> inspect.getfile(db)
'mypath1/lib/db/db.pyc'
>>>
>>> import dart
>>> inspect.getfile(dart)
'mypath2/lib/dart.so'
>>>

My PYTHONPATH contains both mypath1/lib/db and mypath2/lib.

I was under the impression that in order to be able to load modules, the interpreter needs access to a .py file which then calls imp.load_module to load the required shared library (.so file). This is what I see in case of the db module which has a db.py file under mypath1/lib/db. However, dart does not have a .py file under mypath2/lib.

Is it possible to import a module without the .py file as is happening in the case of the dart module ?

解决方案

Python searches for several different files for any given import including a directory by that name and containing an __init__.py, an .so file for pure-native Python modules and .pyc files which can be used even if the .py is removed.

Run strace -o trace_output.txt python to see how this works. Partial example for import md5:

stat("/usr/lib/python2.7/md5", 0x7fff81ff16d0) = -1 ENOENT (No such file or directory)
open("/usr/lib/python2.7/md5.x86_64-linux-gnu.so", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/lib/python2.7/md5.so", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/lib/python2.7/md5module.so", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/lib/python2.7/md5.py", O_RDONLY) = 3

On my setup, it actually searches:

• ~/.local/lib/python2.7/
• /usr/local/lib/python2.7/dist-packages
• /usr/lib/python2.7/dist-packages
• /usr/lib/python2.7/

Within each directory, the pattern of calling stat to find a directory then looking for .so files, then .py is followed.

For more info on writing a purely native python module, see here: https://docs.python.org/2/extending/index.html

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