Question

How can I make the following snipped of code “pythonic”

 tag_list = []
 for d in docs:
        tags = d["tags"]
        for tag in tags:
            if tag not in tag_list:
                tag_list.append(tag)

Answer 1

taglist = set()
for d in docs:
    taglist |= set(d["tags"])
taglist = list(taglist)

or

from itertools import chain
taglist = list(set(chain(*(d["tags"] for d in docs))))

or (thx to @lazy1):

from itertools import chain
taglist = list(set(chain.from_iterable(d["tags"] for d in docs)))

or

import operator
taglist = list(reduce(operator.or_, (set(d["tags"]) for d in docs)))