How to gain complete access to a heroku-postgresql database via python

Question

I made a postrgesql database on heroku. Then I tried to access it via a python script. For that I wrote the following code.

import psycopg2

#connect to the db 
con = psycopg2.connect(
            host = "an_aws_ec2_instance",
            database="d57kjtuarj5li8",
            user = "mmpywqodjzxlzr",
            password = "************************************")

#cursor 
cur = con.cursor()

#execute query
cur.execute("CREATE TABLE accounts (user_id serial PRIMARY KEY, username VARCHAR ( 50 ) UNIQUE NOT NULL, password VARCHAR ( 50 ) NOT NULL, email VARCHAR ( 255 ) UNIQUE NOT NULL, created_on TIMESTAMP NOT NULL, last_login TIMESTAMP)")
cur.execute = ("""SELECT * FROM accounts""")
rows = cur.fetchall()

for r in rows:
    print (r)

#commit the transcation 
con.commit()

#close the cursor
cur.close()

#close the connection
con.close()

But on executing the code, I got the following error.

---> 15 cur.execute = ("""SELECT * FROM accounts""")
     16 rows = cur.fetchall()

AttributeError: 'psycopg2.extensions.cursor' object attribute 'execute' is read-only

Denis Cornehl · Accepted Answer · 2021-03-24 13:16:08Z

1

When you comapare your two SQL lines, there is a major difference.

This calls the method execute on the object cur, with the SQL statement as parameter:

cur.execute("CREATE TABLE accounts (user_id serial PRIMARY KEY, username VARCHAR ( 50 ) UNIQUE NOT NULL, password VARCHAR ( 50 ) NOT NULL, email VARCHAR ( 255 ) UNIQUE NOT NULL, created_on TIMESTAMP NOT NULL, last_login TIMESTAMP)")

This here is something different. Here you are trying to assign a string (the SQL statement) to an attribute (execute), which is read-only on that object.

cur.execute = ("""SELECT * FROM accounts""")
#          THIS

if remove the = from the second statement, you're fine.

answered Mar 24, 2021 at 13:16

Denis Cornehl

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