Replace/delete field using sqlalchemy

Question

Using postgres in python,

How do I replace all fields from the same column that match a specified value? For example, let's say I want to replace any fields that match "green" with "red" in the "Color" column.
How to delete all fields from the same column that match a specified value? For example, I'm trying to deleted all fields that match "green" in the Color column.

Cat Plus Plus · Accepted Answer · 2009-09-27 19:39:37Z

9

Ad1. You need something like this:

session.query(Foo).filter_by(color = 'green').update({ 'color': 'red' })
session.commit()

Ad2. Similarly:

session.query(Foo).filter_by(color = 'green').delete()
session.commit()

You can find the querying documentation here and here.

answered Sep 27, 2009 at 19:39

Cat Plus Plus

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3 Comments

teggy Over a year ago

I think the second answer deletes the entire row. I actually only want to delete the field.

teggy Over a year ago

I tried to use something like this to make field empty but it not seem to work: session.query(Foo).filter_by(color = 'green').update({ 'color': '' })

Cat Plus Plus Over a year ago

session.query(Foo).filter_by(color = 'green').update({ 'color': '' }) should work just fine. Maybe you didn't commit? Anyway, creating the engine with echo = True (or configuring sqlalchemy.engine logger) should help you debug that.

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