Programmatic parsing of a requirements file and importing

importer.py

import subprocess
import sys
from pip import _internal as pip #this seems a little dangerous. as-off 

DEBUG = True

def myprint(string_to_print):
    if DEBUG:
        print(string_to_print)

class PackageImporter:

    def __init__(self,app_name):
        self._appname= app_name
        self._pip_session = app_name +"session"


        # from here: https://stackoverflow.com/questions/1051254/check-if-python-package-is-installed
        reqs = subprocess.check_output([sys.executable, '-m', 'pip', 'freeze'])
        self._installed_packages = [r.decode().split('==')[0] for r in reqs.split()]
        self._incoming_reqs = []


    def run_me(self, incoming_req_txt_file):
        self.__parse_requirements_file(incoming_req_txt_file)
        for pkg in self._incoming_reqs:
            self.__install_package(pkg)


    def __parse_requirements_file(self,req_file):
        for item in pip.req.parse_requirements(req_file, session=self._pip_session):
            myprint("")
            if isinstance(item, pip.req.InstallRequirement):
                myprint("required package: {}".format(item.name))
                self._incoming_reqs.append(item.name)

                if len(str(item.req.specifier)) > 0:
                    myprint("  " + str(item.req.specifier))

                if item.link is not None:
                    myprint("  from: " + item.link.url)
                    myprint("  filename: " + item.link.filename)
                    myprint("  egg: " + item.link.egg_fragment)

                if len(item.options) > 0:
                    for opt_type,opts in item.options.iteritems():
                        myprint("  {}:".format(opt_type))
                        if type(opts) is list:
                            for opt in opts:
                                myprint("    " + opt)
                        elif type(opts) is dict:
                            for k,v in opts.iteritems():
                                myprint("    {}: {}".format(k,v))



    def __install_package(self,package):
        # see here : https://stackoverflow.com/questions/1051254/check-if-python-package-is-installed
        if package not in self._installed_packages:
            # see here http://jelly.codes/articles/python-pip-module/
            try:
                pip.main(["install", package]) 
               #might be better doing this in separate process with 'subprocess'
            except SystemExit as e:
                pass
        else:
            myprint("required package: {} is already on the system :)".format(package))


pkg_importer = PackageImporter('myapp')
pkg_importer.run_me('requirements_new.txt')