The setup_venv3 bash command sets up a python3 virtual environment on a fresh ubuntu install. The file contains quite a few helper functions that make the actual implementation of setup_venv3 rather short.

ubuntu_setup_venv3_standalone.sh

__heredoc__(){ NOOP=; }


has_pymodule(){
    __heredoc__ '''
    Check if a python module is installed. Echos "True" or "False" to the
    command line depending on the result.

    Example:
        source $HOME/local/init/utils.sh
        has_pymodule sys
        has_pymodule fake_module
    '''

    if [ "$2" ]; then
        PYEXE="$1"
        PYMOD="$2"
    else
        PYEXE=python
        PYMOD="$1"
    fi
    pyblock "$PYEXE" "
        try:
            import $PYMOD
            print(True)
        except ImportError:
            print(False)
    "
}


pyblock(){
    __heredoc__ '''
    Executes python code and handles nice indentation.  Need to be slightly
    careful about the type of quotes used.  Typically stick to doublequotes
    around the code and singlequotes inside python code. Sometimes it will be
    necessary to escape some characters.

    Usage:
       pyblock [PYEXE] TEXT

    Args:
       PYEXE : positional arg to specify the python executable.
           if not specified, it defaults to "python"

       TEXT : arbitrary python code to execute

    Notes:
        Capture results from stdout either using using
            (1) dollar-parens: $()
            (2) backticks: ``

    Example:
        source $HOME/local/init/utils.sh
        OUTPUT=$(pyblock "
            import sys
            print(sys.executable)
        ")
        echo "OUTPUT = $OUTPUT"
    '''
    if [ "$2" ]; then
        PYEXE="$1"
        TEXT="$2"
    else
        PYEXE=python
        TEXT="$1"
    fi
    $PYEXE -c "$(codeblock "$TEXT")"
}


codeblock()
{
    if [ "-h" == "$1" ] || [ "--help" == "$1" ]; then 
        # Use codeblock to show the usage of codeblock, so you can use
        # codeblock while you codeblock.
        echo "$(codeblock '
            Unindents code before its executed so you can maintain a pretty
            indentation in your code file. Multiline strings simply begin  
            with 
                "$(codeblock "
            and end with 
                ")"

            Example:
               echo "$(codeblock "
                    a long
                    multiline string.
                    this is the last line that will be considered.
                    ")"
        ')"
    else
        # Prevents python indentation errors in bash
        #python -c "from textwrap import dedent; print(dedent('''$1''').strip('\n'))"
        echo "$1" | python -c "import sys; from textwrap import dedent; print(dedent(sys.stdin.read()).strip('\n'))"
    fi
}


have_sudo(){
    __heredoc__ '''
    Tests if we have the ability to use sudo.
    Returns the string "True" if we do.

    Example:
        HAVE_SUDO=$(have_sudo)
        if [ "$HAVE_SUDO" == "True" ]; then
            sudo do stuff
        else
            we dont have sudo
        fi
    '''

    python -c "$(codeblock "
        import grp, pwd 
        user = '$(whoami)'
        groups = [g.gr_name for g in grp.getgrall() if user in g.gr_mem]
        gid = pwd.getpwnam(user).pw_gid
        groups.append(grp.getgrgid(gid).gr_name)
        print('sudo' in groups)
    ")"
}


ensure_curl(){
    HAVE_SUDO=$(have_sudo)
    if [ "$(which curl)" == "" ]; then
        echo "Need to install curl"
        if [ "$HAVE_SUDO" == "True" ]; then
            sudo apt install curl -y
        else
            echo "Cannot install curl without sudo"
        fi
    fi
}


setup_venv3(){
    __heredoc__ """
    CommandLine:
        source ~/local/init/freshstart_ubuntu.sh && setup_venv3
    """
    # Ensure PIP, setuptools, and virtual are on the SYSTEM
    if [ "$(has_pymodule python3 pip)" == "False" ]; then
    #if [ "$(which pip3)" == "" ]; then
        ensure_curl
        mkdir -p ~/tmp
        curl https://bootstrap.pypa.io/get-pip.py > ~/tmp/get-pip.py

        # Test if we have distutils; if not, install it. 
        python3 -c "from distutils import sysconfig as distutils_sysconfig"
        if [ "$(echo $?)" != "0" ]; then
            sudo apt install python3-distutils -y
        fi

        python3 ~/tmp/get-pip.py --user
    fi
    python3 -m pip install pip setuptools virtualenv -U --user

    #python3 -c "import sys; print(sys.version)"
    #PYVERSUFF=$(python3 -c "import sys; print('.'.join(map(str, sys.version_info[0:3])))")
    #PYVERSUFF=$(python3 -c "import sysconfig; print(sysconfig.get_config_var('LDVERSION'))")
    PYEXE=$(python3 -c "import sys; print(sys.executable)")
    PYVERSUFF=$(python3 -c "import sysconfig; print(sysconfig.get_config_var('VERSION'))")
    PYTHON3_VERSION_VENV="$HOME/venv$PYVERSUFF"
    mkdir -p $PYTHON3_VERSION_VENV
    python3 -m virtualenv -p $PYEXE $PYTHON3_VERSION_VENV 
    python3 -m virtualenv --relocatable $PYTHON3_VERSION_VENV 

    PYTHON3_VENV="$HOME/venv3"
    # symlink to the real env
    ln -s $PYTHON3_VERSION_VENV $PYTHON3_VENV
}