Ubuntu 17.10下Python 2.7虚拟环境无法安装包的问题排查

Hey there! Let's walk through the common pitfalls and fixes when you're trying to set up a Python 2.7 virtual environment alongside an Anaconda Python 3.6.3 installation. Here's what to check and fix:

1. Ensure virtualenv is installed for Python 2.7 #

If you originally installed virtualenv using Anaconda's Python 3 pip, it might be tied to Python 3 by default, which can cause conflicts when targeting Python 2.7.

• First, check which virtualenv you're using:

  which virtualenv
  

  If the path points to your Anaconda bin directory (like ~/anaconda3/bin/virtualenv), it's Python 3-based.

• Fix this by installing virtualenv specifically for Python 2.7 using your system's Python 2.7 pip:

  /usr/bin/python2.7 -m pip install virtualenv
  

  (Replace /usr/bin/python2.7 with the actual path from which python2.7 if it's different.)

2. Double-check your virtualenv creation command #

Make sure you're using the correct, full path to your system's Python 2.7 executable.

• First confirm the path:

  which python2.7
  

• Then create the virtual environment with that exact path:

  virtualenv --python=/usr/bin/python2.7 /path/to/your/project/dir
  

  (Swap /path/to/your/project/dir with your actual project folder path.)

3. Verify the activated environment is using Python 2.7 #

After activating the environment, always confirm you're in the right Python version:

• Activate the environment (Linux/macOS):

  source /path/to/your/project/dir/bin/activate
  

• Check versions:

  python --version  # Should show Python 2.7.x
  pip --version     # Should show pip tied to Python 2.7
  

If these show Python 3, your virtualenv wasn't created correctly—go back to step 2 and ensure you used the right Python 2.7 path.

4. Fix outdated pip for Python 2.7 #

Python 2.7 is end-of-life, and newer pip versions don't support it. If you get errors like SyntaxError or "pip is too old", upgrade pip to the last version compatible with Python 2.7:

pip install pip==20.3.4

5. Resolve package installation errors #

Many modern packages no longer support Python 2.7. If you get errors installing a package, look for the latest version that explicitly supports Python 2.7:

• For example, to install a compatible version of requests:

  pip install requests==2.27.1
  

• Check the package's documentation or PyPI page to find the last Python 2.7-compatible release.

6. Isolate the environment from Anaconda #

If Anaconda's packages are still leaking into your virtual environment, create the env with the --no-site-packages flag to fully isolate it:

virtualenv --python=/usr/bin/python2.7 --no-site-packages /path/to/your/project/dir

内容的提问来源于stack exchange，提问作者Dhruv Marwha