But in almost all of the langauge, TOOWTDI is not strictly enforced, it is merely a highly encouraged convention. For example, why am I allowed to do

    mylist = [x*2 for x in range(1,10)]

but also do

    mylist = []
    for x in range(1,10):
      mylist.append(x*2)

That's two ways to do the same thing, and I bet you would find a lot of the latter in beginner's python code. I think a better choice would to just have a linter which enforced the correct usage of sum() and join(), and not the implementation itself.