Psycopg is the most popular PostgreSQL database adapter for the Python programming language. Its main features are the complete implementation of the Python DB API 2.0 specification and the thread safety (several threads can share the same connection). YugabyteDB has full support for Psycopg2.
Fundamentals of PostgreSQL Psycopg driver
Learn how to establish a connection to YugabyteDB database and begin simple CRUD operations using the steps in Build an Application in the Quick Start section.
Let us break down the quick start example and understand how to perform the common tasks required for Python App development using the PostgreSQL Psycopg driver.
Download the Driver Dependency
If prerequisites are met, you can install psycopg like any other Python package, using
pip to download it from PyPI:
$ pip install psycopg2
setup.py if you have downloaded the source package locally:
$ python setup.py build $ sudo python setup.py install
You can also obtain a stand-alone package, not requiring a compiler or external libraries, by installing the psycopg2-binary package from PyPI:
$ pip install psycopg2-binary
The binary package is a practical choice for development and testing but in production it is advised to use the package built from sources.
Connect to YugabyteDB Database
Python Apps can connect to and query the YugabyteDB database. To do that first import the psycopg2 package.
The Connection details can be provided as a string or a dictionary. Connection String
"dbname=database_name host=hostname port=port user=username password=password"
user = 'username', password='xxx', host = 'hostname', port = 'port', dbname = 'database_name'
Example URL for connecting to YugabyteDB can be seen below.
conn = psycopg2.connect(dbname='yugabyte',host='localhost',port='5433',user='yugabyte',password='yugabyte')
|host||hostname of the YugabyteDB instance||localhost|
|port||Listen port for YSQL||5433|
|user||user for connecting to the database||yugabyte|
|password||password for connecting to the database||yugabyte|
Create a Cursor
To execute any sql commands, a cursor needs to be created after connection is made. It allows Python code to execute PostgreSQL command in a database session. Cursors are created by the
connection.cursor() method: they are bound to the connection for the entire lifetime and all the commands are executed in the context of the database session wrapped by the connection.
cur = conn.cursor()
Tables can be created in YugabyteDB by passing the
CREATE TABLE DDL statement to the
CREATE TABLE IF NOT EXISTS employee (id int PRIMARY KEY, name varchar, age int, language text)
conn = psycopg2.connect(dbname='yugabyte',host='localhost',port='5433',user='yugabyte',password='yugabyte') cur = conn.cursor() cur.execute('CREATE TABLE IF NOT EXISTS employee (id int PRIMARY KEY, name varchar, age int, language varchar)')
Read and Write Data
In order to write data into YugabyteDB, execute the
INSERT statement using the
INSERT INTO employee VALUES (1, 'John', 35, 'Java')
conn = psycopg2.connect(dbname='yugabyte',host='localhost',port='5433',user='yugabyte',password='yugabyte') cur = conn.cursor() cur.execute('INSERT INTO employee VALUES (1, 'John', 35, 'Java')')
In order to query data from YugabyteDB tables, execute the
SELECT statement using
cursor.execute(statement) method followed by
fetchall() fetches all the rows of a query result, returning them as a list of tuples. An empty list is returned if there is no more record to fetch.
SELECT * from employee;
conn = psycopg2.connect(dbname='yugabyte',host='localhost',port='5433',user='yugabyte',password='yugabyte') cur = conn.cursor() cur.execute('SELECT * from employee') rows = cur.fetchall() for row in rows: print("\nQuery returned: %s, %s, %s" % (row, row, row))
Psycopg2 supports several SSL modes, as follows:
|SSL mode||Client driver behavior|
By default, the driver supports the
prefer SSL mode. And in the
require mode, a root CA certificate isn't required to be configured.
verify-full, you need to provide the path to the root CA certificate in the connection string using the
sslrootcert parameter. The default location is
~/.postgresql/root.crt. If the root certificate is in a different file, specify it in the
conn = psycopg2.connect("host=<hostname> port=5433 dbname=yugabyte user=<username> password=<password> sslmode=verify-full sslrootcert=/Users/my-user/Downloads/root.crt")
The difference between
verify-full depends on the policy of the root CA. If you're using a public CA, verify-ca allows connections to a server that somebody else may have registered with the CA. Because of this behavior, you should always use verify-full with a public CA. If you're using a local CA, or even a self-signed certificate, using verify-ca may provide enough protection, but the best security practice is to always use verify-full.