This is a utily script to update the settings.py file in Django projects, based on the contents of the .env file. It also adds code for dotenv support.

update_settings

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# update_settings - Monday, December 23, 2019
__version__ = '1.1.10'

import os, re
from glob import glob
from os.path import basename, dirname, exists, getmtime, join


def main():
	""" Update settings.py with my preferences """
	# Read settings.py
	contents_modified = False
	with open(SETTINGS, 'rt') as infile:
		contents = [x.rstrip() for x in infile.readlines()]

	# Search & Insert
	search_inserts = [
		( "import os", "from dotenv import load_dotenv" ),
		( "BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))",
		  "load_dotenv(os.path.join(BASE_DIR, '.env'))" ),
		( "", "" ),
	]
	for search, insert in search_inserts:
		if not search:
			continue
		s = contents.index(search)
		if s and contents[s + 1] != insert:
			# print(insert)
			contents.insert(s + 1, insert)
			contents_modified = True

	# Search & Replace
	search_replaces = [
		("SECRET_KEY = ", "SECRET_KEY = os.getenv('SECRET_KEY') or "),
		("TIME_ZONE = 'UTC'", "TIME_ZONE = os.getenv('TZ') or 'UTC'"),
		("DEBUG = True", "DEBUG = os.getenv('DEBUG') or False"),
		("", ""),
	]
	for search, replace in search_replaces:
		if not search:
			continue
		for i in range(len(contents)):
			# ToDo: SECRET_KEY, DEBUG = os.getenv()
			if contents[i].startswith(search) and replace not in contents[i]:
				contents[i] = contents[i].replace(search, replace)
				contents_modified = True
		# ToDo: TEMPLATES.DIRS = [ os.path.join(BASE_DIR, 'templates'), ]
		# ToDo: TIME_ZONE = 'UTC' ==> TIME_ZONE = os.getenv('TZ') or 'America/Toronto'
		# ToDo: LOGIN URLs, etc.

	# Section Processing - TEMPLATES
	section = 'TEMPLATES = '
	inside_templates = False
	for i in range(len(contents)):
		if contents[i].startswith(section):
			# print('Found TEMPLATES')
			inside_templates = True
		if inside_templates:
			search = "'DIRS': [],"
			replace = "'DIRS': [ os.path.join(BASE_DIR, 'templates'), ],"
			if contents[i].strip() == search and replace not in contents[i]:
				contents[i] = contents[i].replace(search, replace)
				contents_modified = True
			if contents[i] == ']':
				inside_templates = False

	# Process .env file
	with open('.env', 'rt') as envfile:
		# Only load non-blank lines that aren't comments and strip newline characters
		envlines = [x.rstrip() for x in envfile.readlines() if x != '\n' and not x.startswith('#')]
	# print(envlines)

	varnames = []
	for line in envlines:
		varnames.append(line.split('=')[0])
	# print(varnames)
	vars_regex = re.compile(r'(%s)\s*=' % '|'.join(varnames))
	# print("RegEx:", vars_regex)
	found = []
	for i in range(len(contents)):
		line = contents[i]
		match = vars_regex.search(line)
		if match:
			word = match[0].split('=')[0].strip()
			found.append(word)
	not_found = []
	for v in varnames:
		if v not in found:
			not_found.append(v)
	if not_found:
		addlines = [x + " = os.getenv('%s')" % x for x in not_found]
		addlines.insert(0,  "\n\n# Additional environment variables in .env added by 'update_settings'")
		contents += addlines + ['\n\n\n',]
		contents_modified = True

	# Process any changes
	if contents_modified:
		# Remove duplicate lines from file
		newlines = []
		lastline = ''
		for c in contents:
			if c != lastline:
				newlines.append(c)
				if c.strip() != '':
					lastline = c
		contents = newlines

		# Write updated file to disk
		with open(WORKFILE, 'wt') as outfile:
			outfile.writelines([ x + os.linesep for x in contents ])
		os.renames(SETTINGS, SETTINGS + '~')
		os.renames(WORKFILE, SETTINGS)
	else:
		print("No modifications detected.")
	return


def init():
	""" Prepare for main() processing """
	global SETTINGS, WORKFILE
	settings_py = glob('**/%s' % SETTINGS, recursive=True)
	if not settings_py:
		raise FileNotFoundError(SETTINGS)
	SETTINGS = settings_py[0]
	parts = SETTINGS.split(os.sep)
	parts[-1] = '.' + parts[-1]
	if not exists(SETTINGS):
		raise FileNotFoundError(SETTINGS)
	WORKFILE = os.sep.join(parts)
	return


def eoj():
	if exists(BACKUP_FILE):
		os.system('meld %s %s' % (BACKUP_FILE, SETTINGS))
	return


def debug_breakpoint():
	pass
	return


if __name__ == '__main__':
	SETTINGS = 'settings.py'
	WORKFILE = '.' + SETTINGS
	BACKUP_FILE = SETTINGS + '~'
	init()
	main()
	eoj()