python postgresql fetcha code example

Example 1: psycopg2 query

>>> import psycopg2

# Connect to an existing database
>>> conn = psycopg2.connect("dbname=test user=postgres")

# Open a cursor to perform database operations
>>> cur = conn.cursor()

# Execute a command: this creates a new table
>>> cur.execute("CREATE TABLE test (id serial PRIMARY KEY, num integer, data varchar);")

# Pass data to fill a query placeholders and let Psycopg perform
# the correct conversion (no more SQL injections!)
>>> cur.execute("INSERT INTO test (num, data) VALUES (%s, %s)",
...      (100, "abc'def"))

# Query the database and obtain data as Python objects
>>> cur.execute("SELECT * FROM test;")
>>> cur.fetchone()
(1, 100, "abc'def")

# Make the changes to the database persistent
>>> conn.commit()

# Close communication with the database
>>> cur.close()
>>> conn.close()

Example 2: postgresql psycopg2 select single value

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import psycopg2
import sys

con = None

try:

    con = psycopg2.connect(database='testdb', user='postgres',
        password='s$cret')

    cur = con.cursor()
    cur.execute('SELECT version()')

    version = cur.fetchone()[0]
    print(version)

except psycopg2.DatabaseError as e:

    print(f'Error {e}')
    sys.exit(1)

finally:

    if con:
        con.close()