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"""

Beginner PostgreSQL example using psycopg.

This script expects a DATABASE_URL environment variable, for example:

export DATABASE_URL="postgresql://myuser:mypassword@localhost:5432/my_first_python_app"

Then run:

../venv/bin/python python-language/postgres_basics.py

"""

from __future__ import annotations

import os

import psycopg

def get_database_url() -> str:

database_url = os.getenv("DATABASE_URL")

if not database_url:

raise RuntimeError(

"DATABASE_URL is not set. Example: "

"postgresql://myuser:mypassword@localhost:5432/my_first_python_app"

)

return database_url

def run_demo() -> None:

database_url = get_database_url()

with psycopg.connect(database_url) as conn:

with conn.cursor() as cur:

cur.execute(

"""

CREATE TABLE IF NOT EXISTS lessons (

id SERIAL PRIMARY KEY,

title TEXT NOT NULL,

duration_minutes INTEGER NOT NULL,

completed BOOLEAN NOT NULL DEFAULT FALSE

)

"""

)

cur.execute(

"""

INSERT INTO lessons (title, duration_minutes, completed)

VALUES (%s, %s, %s)

""",

("PostgreSQL Basics", 45, False),

)

cur.execute(

"""

SELECT id, title, duration_minutes, completed

FROM lessons

ORDER BY id

"""

)

rows = cur.fetchall()

print("Saved lessons:")

for row in rows:

print(row)

if __name__ == "__main__":

run_demo()