What's the difference between filter and filter_by in SQLAlchemy?

Question

Hello everyone!

Could anyone explain the difference between filter and filter_by functions in SQLAlchemy? I am confused and can't really see the difference. Which one should I be using?

Thanks, Boda Cydo

Answer 1

filter_by is used for simple queries on the column names like

db.users.filter_by(name='Joe')

The same can be accomplished with filter by writing

db.users.filter(db.users.name=='Joe')

but you can also write more powerful queries containing expressions like

db.users.filter(or_(db.users.name=='Ryan', db.users.country=='England'))

Answer 2

filter_by uses keyword arguments, whereas filter allows pythonic filtering arguments like filter(User.name="john")

Answer 3

We actually had these merged together originally, i.e. there was a "filter"-like method that accepted *args and **kwargs, where you could pass a SQL expression or keyword arguments (or both). I actually find that a lot more convenient, but people were always confused by it, since they're usually still getting over the difference between column == expression and keyword = expression. So we split them up.