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:
fordamninmap(teardown,connections):pass
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?
I'm a Sr. Software Engineer at Flashpoint. I specialize in Python and Go, building functional, practical, and maintainable web systems leveraging Kubernetes and the cloud. Blog opinions are my own.
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:
teardown(connection)
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.
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:
My code didn't work, and I spent 1 hour to realize the
teardownfunction never run. I end up with:In python3,
mapreturns an iterator and functions inside never run until being iterated on. In my opinion, this is inconsistent behavior: Python is sync by default, somapshould be sync, asynchronous map should bemapAsyncor be imported fromasyncio. 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:
teardown(connection)
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,reduceandfilter. 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!