Python list comprehension Django objects

Question

I am developing a dictionary Django app where Definition s have Tag s. I have written this generic function to collect all Tag s from a list of Definition s.

This is my current working version:

def get_tags(definitions):
    tags = []
    for d in definitions:
        tags += d.tags.all()
    return tags

I was trying to accomplish the same using Python's list comprehension:

tags = []
return [tags.extend(d.tags.all()) for d in definitions]

This code however does not work yet. What am I missing?

Is there an even slicker way to do this in just one line without creating the tags variable, perhaps using yield statement?

Answer 1

you need to iterate over all the elements d.tags.all() , and thus need a nested list comp:

tags = [t for d in definitions for t in d.tags.all()]

this is just the list comprehension version of:

tags = []
for d in definitions:
    for t in d.tags.all():
        tags.append(t)