> For the complete documentation index, see [llms.txt](https://jarvisma.gitbook.io/pythonlearn/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://jarvisma.gitbook.io/pythonlearn/5.5-venv/chapter5.5.3.md).

# 5.5.3 工作原理

其实 venv 的工作原理非常简单，完全集中在 `bin/active` 这个简单的脚本中，它的核心部分如下：

```
deactive () {
    # 恢复环境
}

VIRTUAL_ENV="/Users/JarvisMa/Desktop/testvenv"
export VIRTUAL_ENV

_OLD_VIRTUAL_PATH="$PATH"
PATH="$VIRTUAL_ENV/bin:$PATH"
export PATH
```

可见它把当前目录标记为 `VIRTUAL_ENV`，然后添加到系统的 `PATH` 最前面，这样我们执行 `pip` 命令时，第三方的包就会被安装虚拟环境内的 `site-packages` 文件夹中，不会与系统的干扰。


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