Python script to manage a simple Journal system (with a template)

journal.py

#!/bin/env python3
import os
import datetime

EDIT_CMD = "vim {{ path }}"
BASE_PATH = "posts"

def template(s, data):
	"""
	a very simple template evaluation method
	"""
	ret = ""

	buf = ""
	inside = False
	i = 0
	while i < len(s):
		lookahead = s[i:i+2]
		if lookahead in ("{{", "}}"):
			inside = not inside

			if inside:
				buf = ""
			else:
				ret += data.get(buf.strip(), "??")

			i += len(lookahead)
			continue

		if inside:
			buf += s[i]
		else:
			ret += s[i]
			
		i += 1
	
	return ret

# https://stackoverflow.com/a/50992575/5013267
def make_ordinal(n):
    """
    Convert an integer into its ordinal representation::

        make_ordinal(0)   => '0th'
        make_ordinal(3)   => '3rd'
        make_ordinal(122) => '122nd'
        make_ordinal(213) => '213th'
    """
    n = int(n)
    suffix = ['th', 'st', 'nd', 'rd', 'th'][min(n % 10, 4)]
    if 11 <= (n % 100) <= 13:
        suffix = 'th'
    return str(n) + suffix

def get_long_date(date):
	return date.strftime("%a ") + make_ordinal(date.day) + date.strftime(" of %B, %Y")

def write_page(date):
	file_path = os.path.join(BASE_PATH, date.strftime("%Y-%m-%d.md"))

	if not os.path.isfile(file_path):
		with open(file_path, "w") as new_file:
			with open("res/templ.md", "r") as templ_file:
				new_file.write(template(templ_file.read(), {
					"longdate": get_long_date(date),
					"date": date.strftime("%x"),
				}))
	
	return file_path

def edit_page(date):
	file_path = write_page(date)
	os.system(template(EDIT_CMD, {
		"path": file_path,
	}))


if __name__ == "__main__":
	os.makedirs(BASE_PATH, exist_ok=True)
	edit_page(datetime.date.today())