Functions to install required dependencies for a python script.

require_dependency.py

#!/usr/bin/env python

import subprocess
import sys


def run_command(command):
    return subprocess.check_output(command, shell=True, stderr=subprocess.STDOUT).strip()


def get_dependencies():
    return run_command("pip list --format=columns")


def check_pip():
    result = run_command("easy_install")
    if "command not found" not in result:
        print "easy_install found, installing pip..."
        run_command("sudo easy_install pip")
        return

    print "No quick tool found to install dependencies. Please check if you have Python 2.7 installed and then " \
          "install Brew (https://brew.sh/) and run `brew install python`."

    print "Alternatively, if Python is installed, consider manually installing pip as described in " \
          "https://pip.readthedocs.io/en/stable/installing/"


def upgrade_dependency(dependency):
    run_command("pip install {} -U".format(dependency))
    print "Done."


def check_dependencies(dependency, dependency_version):
    result = get_dependencies()

    # Check pip
    lib_version = None
    if "command not found" in result:
        print "Pip not found"
        check_pip()
        result = get_dependencies()
        if "command not found" in result:
            sys.exit(2)

    for line in result.splitlines():
        if dependency in line:
            lib_version = line

    # Check lib installed
    if lib_version is None:
        print "No version of {} found, installing...".format(dependency)
        upgrade_dependency(dependency)

    # Check lib updated
    elif lib_version.split()[1] != dependency_version:
        print "Wrong version of {} found: {}, upgrading...".format(dependency, lib_version.split()[1])
        upgrade_dependency(dependency)
    else:
        print dependency + " up to date."