使用Brew为Python3安装boost-python时检测到Python2.7的问题咨询

Hey there, let's break down why your brew install is still targeting Python 2.7 instead of 3.5, and how to fix this issue.

Why This Happens #

When you run brew install boost-python --with-python3, Brew's default formula for boost-python still prioritizes your system's default Python (which is 2.7) to execute the ./bootstrap script. The --with-python3 flag enables Python 3 support, but it doesn't explicitly tell the bootstrap process to use Python 3 as its build interpreter. That’s why you see --with-libraries=python --with-python=python instead of python3 in the bootstrap command.

Step-by-Step Solutions #

Option 1: Use Environment Variables to Force Python 3

This method explicitly tells Brew and the boost bootstrap script exactly which Python version to use:

1. First, clean up any existing boost installations to avoid conflicts:

   brew uninstall --force boost boost-python
   

2. Set environment variables pointing to your Python 3 installation:

   export PYTHON=/usr/local/bin/python3
   export PYTHON_INCLUDE=$(python3 -c "import sysconfig; print(sysconfig.get_path('include'))")
   export PYTHON_LIB=$(python3 -c "import sysconfig; print(sysconfig.get_config_var('LIBDIR'))")
   

3. Run the install command again with your original flags:

   brew install --build-from-source --fresh -vd boost-python --with-python3
   

Option 2: Use Brew's Dedicated Python 3 Boost Formula

Most newer Brew versions have a separate formula for Python 3-specific boost bindings. This is the simplest and most reliable approach:

brew install boost-python3

This formula is pre-configured to build against Python 3, so you won’t need to mess with environment variables or bootstrap flags.

Option 3: Manually Adjust the Bootstrap Command (Advanced)

If the above options don’t work, you can temporarily modify Brew's boost-python formula to hardcode Python 3 in the bootstrap step:

1. Edit the formula file:

   brew edit boost-python
   

2. Look for the section where ./bootstrap is called. Replace any instance of --with-python=python with --with-python=python3.
3. Save the file and run your original install command.

Note: This change will be overwritten when Brew updates the formula, so it’s only a temporary fix.

Verification #

After installation, confirm the bindings are linked to Python 3 by checking the library path:

ls -la /usr/local/lib/libboost_python*.dylib

You should see files ending with 35 (matching your Python 3.5 version) instead of 27.

内容的提问来源于stack exchange，提问作者John M.