re: Rust, Iterators, and Skill Regression VIEW POST


Last week I was fucked up, I need to tear down some connection in Python and this is what spawned out of my normal functional programming brain:

map(teardown, connections)

My code didn't work, and I spent 1 hour to realize the teardown function never run. I end up with:

for damn in map(teardown, connections):

In python3, map returns an iterator and functions inside never run until being iterated on. In my opinion, this is inconsistent behavior: Python is sync by default, so map should be sync, asynchronous map should be mapAsync or be imported from asyncio. Why makes such simple thing so surprising?


Well in general, I would say that in Python at least, you should probably almost never need the map function. If you’re using map, you probably want a for loop or a list comprehension. Especially if you’re not using the result of the teardown function, it probably ought to be:

for connection in connections:

What do you think?


Thank you, I knew it and did it since the first days I learn programming. It's more a matter of preference, the functional programming way seems more natural and straightforward to me.

IFAIK, FP isn't a recommended paradigm in Python, even Guido has said he wants to remove map, reduce and filter. Now I think he's right, anyone wishes for FP favor should use a third party module rather than rely on the standard library.


A better name for this behaviour would be lazy instead of asynchronous.

An async operation generally means stuff happening "behind the scenes/at the same time", while a lazy operation delivers results "on demand", which is the case for the iterators.


Yeah, lazy evaluation in contrast to eager evaluation.

Thank you!

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