psycopg2 export DB to csv with column names - python-3.x

Question

I'm using psycopg2 to connect to postgre DB, and to export the data into CSV file.
This is how I made the export DB to csv:
def export_table_to_csv(self, table, csv_path):
sql = "COPY (SELECT * FROM %s) TO STDOUT WITH CSV DELIMITER ','" % table
self.cur.execute(sql)
with open(csv_path, "w") as file:
self.cur.copy_expert(sql, file)
But the data is just the rows - without the column names.
How can I export the data with the column names?
P.S. I am able to print the column names:
sql = '''SELECT * FROM test'''
self.cur.execute(sql)
column_names = [desc[0] for desc in self.cur.description]
for i in column_names:
print(i)
I want the cleanest way to do export the DB with columns name (i.e. I prefer to do this in one method, and not rename columns In retrospect).

Answer 1

As I said in my comment, you can add HEADER to the WITH clause of your SQL:
sql = "COPY (SELECT * FROM export_test) TO STDOUT WITH CSV HEADER"
By default, comma delimiters are used with CSV option so you don't need to specify.
For future Questions, you should submit a minimal reproducible example. That is, code we can directly copy and paste and run. I was curious if this would work so I made one and tried it:
import psycopg2
conn = psycopg2.connect('host=<host> dbname=<dbname> user=<user>')
cur = conn.cursor()
# create test table
cur.execute('DROP TABLE IF EXISTS export_test')
sql = '''CREATE TABLE export_test
(
id integer,
uname text,
fruit1 text,
fruit2 text,
fruit3 text
)'''
cur.execute(sql)
# insert data into table
sql = '''BEGIN;
insert into export_test
(id, uname, fruit1, fruit2, fruit3)
values(1, 'tom jones', 'apple', 'banana', 'pear');
insert into export_test
(id, uname, fruit1, fruit2, fruit3)
values(2, 'billy idol', 'orange', 'cherry', 'strawberry');
COMMIT;'''
cur.execute(sql)
# export to csv
fid = open('export_test.csv', 'w')
sql = "COPY (SELECT * FROM export_test) TO STDOUT WITH CSV HEADER"
cur.copy_expert(sql, fid)
fid.close()
And the resultant file is:
id,uname,fruit1,fruit2,fruit3
1,tom jones,apple,banana,pear
2,billy idol,orange,cherry,strawberry