virtualenv 是如何工作的? [英] How does virtualenv work?

问题描述

我检查了 activate 脚本，在我看来它所做的就是:

I checked the activate script and it looks to me all it does is:

• 设置 VIRTUAL_ENV 环境
• 在 PATH 前面附加 $VIRTUAL_ENV/bin

virtualenv 如何通过这些提供神奇的虚拟环境?我想念什么?

How does virtualenv provide that magical virtual environment by these? What do I miss?

推荐答案

我将描述基本过程，这是我从 @jcollado 链接的演示文稿中学到的.

I will describe the basic process, which I learned from the presentation @jcollado linked to.

Python 启动时，会查看二进制文件的路径及其前缀.

When Python starts, it looks at the path of the binary, and the prefixes thereof.

假设您的 virtualenv 是 /home/blah/scratch.Python 进程知道它是从 /home/blah/scratch/bin/python 执行的(通常只是你系统 python 二进制文件 /usr/bin/python 的副本)) 并且它知道自己的版本 XY 因为它已编译到其中.然后 Python 按以下顺序查找 lib/pythonX.Y/os.py:

So let's say your virtualenv is /home/blah/scratch. The Python process knows it was executed from /home/blah/scratch/bin/python (which is usually just a copy of your system python binary /usr/bin/python) and it knows its own version X.Y because it's compiled into it. Then Python looks for lib/pythonX.Y/os.py in this order:

/home/blah/scratch/bin/lib/pythonX.Y/os.py
/home/blah/scratch/lib/pythonX.Y/os.py    <-- this file should exist
/home/blah/lib/pythonX.Y/os.py
/home/lib/pythonX.Y/os.py
/lib/pythonX.Y/os.py

它停在 /home/blah/scratch/lib/pythonX.Y/os.py 因为它是第一个实际存在的文件.如果没有，Python 会继续寻找.然后它基于此设置 sys.prefix.它使用类似的过程设置sys.exec_prefix，然后根据这些构造sys.path.

It stops at /home/blah/scratch/lib/pythonX.Y/os.py because it's the first file that actually exists. If it didn't, Python would keep looking. It then sets sys.prefix based on this. It uses a similar process to set sys.exec_prefix, and then sys.path is constructed based on these.

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