How to update existing table rows in SQLAlchemy in Python?

In this article, we are going to see how to use the UPDATE statement in SQLAlchemy against a PostgreSQL database in Python.

Creating table for demonstration:

Import necessary functions from the SQLAlchemy package. Establish connection with the PostgreSQL database using create_engine() function as shown below, create a table called books with columns book_id and book_price. Insert record into the tables using insert() and values() function as shown.

Output:

Update table elements in SQLAlchemy

updating table elements have a slightly different procedure than that of a conventional SQL query which is  shown below

from sqlalchemy import update
upd = update(tablename)
val = upd.values({"column_name":"value"})
cond = val.where(tablename.c.column_name == value)

Get the books to table from the Metadata object initialized while connecting to the database. Pass the update query to the execute() function and get all the results using fetchall() function. Use a for loop to iterate through the results.

The SQLAlchemy query shown in the below code updates the "fiction" genre as "sci-fi" genre this will effectively update multiple rows at one go. Then, we can write a conventional SQL query and use fetchall() to print the results to check whether the table is updated properly.

Output: