OpenMDAO入门：pip安装旧版本后如何激活虚拟环境？

No worries at all—this is a super common mix-up when switching from the old installation scripts to standard pip installs! Let me break this down for you:

为什么pip安装后没有专属虚拟环境文件夹？ #

The old go-openmdao-xx.py scripts were designed to automatically create a dedicated virtual environment for OpenMDAO during installation, which is why you got that openmdao-0.xx.x folder with an activation script.

But when you use pip install openmdao==1.7.4 directly, pip doesn't create a new virtual environment for you by default. It installs the package into whichever Python environment you're currently using (this could be your global system Python, or an existing virtual environment you had already activated).

两种解决方法： #

1. 创建并激活一个专属的虚拟环境（推荐，避免包冲突）

If you want a clean, isolated environment for this old OpenMDAO version (just like the script gave you), follow these steps:

• Create the virtual environment (using Python's built-in venv module, which comes with Python 3.3+):

  python -m venv openmdao-1.7.4-env
  

  You can replace openmdao-1.7.4-env with any folder name you prefer.
• Activate the environment:
  • On Linux/macOS:

    source openmdao-1.7.4-env/bin/activate
    

  • On Windows (Command Prompt):

    openmdao-1.7.4-env\Scripts\activate.bat
    

  • On Windows (PowerShell):

    openmdao-1.7.4-env\Scripts\Activate.ps1
    

• Once activated, install the old OpenMDAO version into this environment:

  pip install openmdao==1.7.4
  

  Now you'll have a dedicated folder for the environment, just like the old script provided.

2. 使用已安装OpenMDAO的现有环境

If you already installed the package into your global Python or another existing virtual environment, you don't need a "new" activation script—just make sure you're using that environment:

• 要确认OpenMDAO的安装位置，运行：

  pip show openmdao
  

  查看Location行就能确认它在哪个环境里。
• 如果它在全局环境中，你可以直接用系统Python运行OpenMDAO（不过不推荐这种方式，因为可能和其他包产生冲突）。

内容的提问来源于stack exchange，提问作者Tim Camp