pandas save csv in postgresql python code example

Example 1: how to save query data into dataframe pscopg2

import pandas as pd
import pandas.io.sql as sqlio
import psycopg2

conn = psycopg2.connect("host='{}' port={} dbname='{}' user={} password={}".format(host, port, dbname, username, pwd))
sql = "select count(*) from table;"
dat = sqlio.read_sql_query(sql, conn)
conn = None

Example 2: run postgresql dump to csv

\copy (SELECT * FROM persons) to 'C:\tmp\persons_client.csv' with csv

Example 3: postgresql export output table as a csv

COPY table_name TO 'file_name.csv' DELIMITER ',' CSV HEADER;