Actually, now that I think about it, with this new(-ish) (in)famous walrus operator and itertools recipes, I could sort of emulate reduce using gen expr

First, I will need to steal a "consume" function from Itertools Recipes [0]:

    from collections import deque
    from itertools import islice
    
    
    def consume(iterator, n=None):
        "Advance the iterator n-steps ahead. If n is None, consume entirely."
        # Use functions that consume iterators at C speed.
        if n is None:
            deque(iterator, maxlen=0)
        else:
            next(islice(iterator, n, n), None)

Isn't it a bit weird, that the fastest and easiest way to consume an iterator entirely is to feed it to a zero length deque? It is weird, but it was just an apéritif, lets move to the main course:

    lst = [1, 2, 3]
    acc = 0
    consume((acc := acc + item for item in lst))  # this is the actual reduce
    print(acc)

This is the line where the actual `reduce`ing happens:

    consume((acc := acc + item for item in lst))

Basically, we use the fact that a "walrus" expression has a side effect and we just throw away the actual results of the iterator, because we don't need them.

Is it more readable then normal reduce? I'm not sure. If I seen it in the actual production code, it would certainly raised my eyebrows. It is not a part of the normal Python "vocab" - a set of idioms that are considered "pythonic" and that you expect every Python dev to intuitively understand, so I would be very cautious in using it in the code that is intended to be read by other people.

Why did I do it? I don't know, just a fun "what if?" thought experiment.

[0] https://docs.python.org/3/library/itertools.html#itertools-r...