如何用Homebrew卸载Python2.7.10？保留Python3.7解决环境问题

Hey there! Let's work through this Python version problem step by step. You've got Python 2.7.10 (the system default) and Python 3.7.2_1 installed, but can't use virtualenv or Flask—so you want to either remove Python 2.7 entirely or wipe all Python versions and reinstall 3.7. Here are two solid Homebrew-based solutions:

Option 1: Keep Python 3.7, Remove Python 2.7 (Proceed with Caution) #

First, a critical note: The Python 2.7 that comes pre-installed with Mac 10.14 is tied to some system tools. Deleting it outright might break things like older system scripts, so think carefully before going this route. If you're set on it, here's how:

1. Verify your Homebrew Python 3.7 installation
   First, make sure your existing Python 3.7 is healthy:

   brew info python@3.7
   

   Jot down the installation path (usually /usr/local/Cellar/python@3.7/3.7.2_1) for reference.

2. Uninstall Homebrew-installed Python 2.7 (if you have it)
   Check if you installed Python 2 via Homebrew:

   brew list | grep python@2
   

   If it shows up, remove it completely:

   brew uninstall --force python@2
   

   The --force flag ensures all associated files are deleted.

3. Handle the system-default Python 2.7
   Instead of deleting it directly (risky!), we can back it up and redirect the python command to 3.7:

   • Back up the system Python first:

     sudo mv /usr/bin/python /usr/bin/python2.7.backup
     

   • Create a symlink to Python 3.7 so python calls it by default:

     sudo ln -s /usr/local/bin/python3 /usr/bin/python
     

   If you absolutely must delete the system Python 2.7 files (not recommended), you can run these commands—but be aware this might break system tools:

   sudo rm -rf /Library/Frameworks/Python.framework/Versions/2.7
   sudo rm -rf /usr/bin/python2.7
   sudo rm -rf /usr/bin/pip2.7
   

   If you run into issues later, restore the backup with:

   sudo mv /usr/bin/python2.7.backup /usr/bin/python
   

Option 2: Wipe All Python Versions, Reinstall Python 3.7 (Safer Choice) #

This is the more reliable approach because it avoids touching the system's default Python entirely. Let's clean everything up and start fresh:

1. Uninstall all Homebrew Python packages
   List all Python-related packages installed via Homebrew:

   brew list | grep python
   

   Uninstall them all with force to remove every trace:

   brew uninstall --force python@2 python@3.7 python
   

2. Clean up leftover files
   Delete residual Python files from user and system directories:

   rm -rf ~/Library/Python
   sudo rm -rf /Library/Frameworks/Python.framework
   rm -rf ~/.pip
   rm -rf ~/.cache/pip
   

3. Reinstall Python 3.7 via Homebrew
   First, update Homebrew to make sure you get the correct version:

   brew update
   

   Install your desired Python 3.7 version:

   brew install python@3.7
   

   Confirm the installation path with:

   which python3
   

   It should show /usr/local/bin/python3.

4. Set Python 3.7 as the default
   Add these lines to your shell config file (either ~/.bash_profile for Bash or ~/.zshrc for Zsh) to make python and pip default to 3.7:

   echo 'export PATH="/usr/local/opt/python@3.7/bin:$PATH"' >> ~/.bash_profile
   echo 'alias python="python3"' >> ~/.bash_profile
   echo 'alias pip="pip3"' >> ~/.bash_profile
   

   Refresh the config to apply changes immediately:

   source ~/.bash_profile
   

5. Verify and test
   Restart your terminal, then check the versions:

   python --version
   pip --version
   

   Both should show Python 3.7.2. Now you can install virtualenv and Flask without issues:

   pip install virtualenv flask
   

Final Notes #

• Option 2 is highly recommended because it avoids messing with system components that could cause unexpected problems.
• If you go with Option 1 and run into system errors, restoring the backed-up Python 2.7 file should fix things.

内容的提问来源于stack exchange，提问作者Eddie Avinashi