Install Python package at runtime

install_packages.py

import pkg_resources
import subprocess
import sys
import importlib
import pprint

def install(package):    
    print(f'\n=======> Checking status of {package}:', flush=True)
    try:
        dist = pkg_resources.get_distribution(package)
        print('{} ({}) is installed'.format(dist.key, dist.version), flush=True)
    except pkg_resources.DistributionNotFound:
        print('{} is NOT installed'.format(package), flush=True)
        subprocess.check_call([sys.executable, "-m", "pip", "install", package])
        # After installation, import the module and print its version
        try:
            pkg = importlib.import_module(package)
            print(f'{package} ({pkg.__version__}) is installed')
        except ImportError:
            print(f"Failed to import {package}")

print (f"\n\n\n=========================================\nReport versions, and install Python packages, if needed.\n", flush=True)
install('flask')
install('gunicorn')
install('docker')
print (f"\n\nPackages are ready for use.\n=========================================\n\n", flush=True)

# Now that we have ensured Flask is installed, we can import it and run our main program
from flask import Flask, request, Response, redirect, render_template