Disclaimer: i just posted this same answer to stack overflow:

https://stackoverflow.com/questions/2812520/pip-dealing-with-multiple-python-versions/50319252

Here is my take on the problem. Works for Python3. The main features are:

• Each Python version is compiled from source
• All versions are installed locally
• Does not mangle your system's default Python installation in any way
• Each Python version is isolated with virtualenv

The steps are as follows:

0. If you have several extra python versions installed in some other way, get rid of them, e.g., remove $HOME/.local/lib/python3.x, etc. (also the globally installed ones). Don't touch your system's default python3 version though.

1. Download source for different python versions under the following directory structure:

    $HOME/
        python_versions/ : download Python-*.tgz packages here and "tar xvf" them.  You'll get directories like this:
          Python-3.4.8/
          Python-3.6.5/
          Python-3.x.y/
          ...
   

2. At each "Python-3.x.y/" directory, do the following (do NOT use "sudo" in any of the steps!):

    mkdir root
    ./configure --prefix=$PWD/root 
    make -j 2
    make install
    virtualenv --no-site-packages -p root/bin/python3.x env
   

3. At "python_versions/" create files like this:

    env_python3x.bash:
   
    #!/bin/bash
    echo "type deactivate to exit"
    source $HOME/python_versions/Python-3.x.y/env/bin/activate
   

4. Now, anytime you wish to opt for python3.x, do

    source $HOME/python_versions/env_python3x.bash
   

to enter the virtualenv

6. While in the virtualenv, install your favorite python packages with

    pip install --upgrade package_name
   

7. To exit the virtualenv and python version just type "deactivate"

i just posted this same answer to stack overflow:

https://stackoverflow.com/questions/2812520/pip-dealing-with-multiple-python-versions/50319252

(see that one for a more up-to-date answer)

Here is my take on the problem. Works for Python3. The main features are:

• Each Python version is compiled from source
• All versions are installed locally
• Does not mangle your system's default Python installation in any way
• Each Python version is isolated with virtualenv

The steps are as follows:

0. If you have several extra python versions installed in some other way, get rid of them, e.g., remove $HOME/.local/lib/python3.x, etc. (also the globally installed ones). Don't touch your system's default python3 version though.

1. Download source for different python versions under the following directory structure:

    $HOME/
        python_versions/ : download Python-*.tgz packages here and "tar xvf" them.  You'll get directories like this:
          Python-3.4.8/
          Python-3.6.5/
          Python-3.x.y/
          ...
   

2. At each "Python-3.x.y/" directory, do the following (do NOT use "sudo" in any of the steps!):

    mkdir root
    ./configure --prefix=$PWD/root 
    make -j 2
    make install
    virtualenv --no-site-packages -p root/bin/python3.x env
   

3. At "python_versions/" create files like this:

    env_python3x.bash:
   
    #!/bin/bash
    echo "type deactivate to exit"
    source $HOME/python_versions/Python-3.x.y/env/bin/activate
   

4. Now, anytime you wish to opt for python3.x, do

    source $HOME/python_versions/env_python3x.bash
   

to enter the virtualenv

6. While in the virtualenv, install your favorite python packages with

    pip install --upgrade package_name
   

7. To exit the virtualenv and python version just type "deactivate"