A python script to create a database if it does not exist with psycopg2 & Postgres.

ph_create_if_not_exists.py

from psycopg2 import connect, extensions, sql, OperationalError
import re

POSTGRES_PASSWORD = 'mypasswd'
POSTGRES_USER     = 'myuser'
POSTGRES_DB       = 'mytest12'

connect_string = f"postgres://{POSTGRES_USER}:{POSTGRES_PASSWORD}@localhost"
db_connect_string = f"{connect_string}/{POSTGRES_DB}"

try:
  engine = connect(db_connect_string)
except OperationalError as e:
  if e.args:
    msg = e.args[0]
    m = re.match('^FATAL:.*database.*does not exist\s', e.args[0], re.IGNORECASE)
    if m and m.endpos == len(msg):
      engine = connect(f'{connect_string}/postgres')
      engine.set_isolation_level(extensions.ISOLATION_LEVEL_AUTOCOMMIT)
      cursor = engine.cursor()
      cursor.execute(sql.SQL("CREATE DATABASE {}").format(sql.Identifier(POSTGRES_DB)))
      cursor.close()
      engine.close()
      engine = connect(db_connect_string)
    else:
      raise

print(f'Connected to: {db_connect_string}')