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Query Your Python Lists

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84 points mkalioby | 2 comments | 15 Nov 24 06:18 UTC | HN request time: 0.397s | source
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abdullahkhalids ◴[20 Nov 24 05:08 UTC] No.42190985[source]▶
I don't understand why numeric filters are included. The library is written in python, so shouldn't a lambda function based filter be roughly as fast but much easier/clearer to write.
replies(2): >>42191496 #>>42192896 #
yunohn ◴[20 Nov 24 11:32 UTC] No.42192896[source]▶
AFAICT this should filter in one pass, so it would be faster than multiple lambdas, or this plus a lambda for numeric.
replies(1): >>42199784 #
me-vs-cat ◴[21 Nov 24 00:38 UTC] No.42199784[source]▶
If you are concerned that your Python is making single-digit extra function calls, then you should be using a different language. (However, you might want a C extension that can be used from Python.)

That said, it's trivial to apply multiple filter lambdas in one pass -- the most natural way is a comprehension.

Still, you might be surprised by how fast filter(cond_1, filter(cond_2, data)) actually is. The OP didn't present that performance comparison, nor can I see any reason they gave to avoid comprehensions.

replies(1): >>42205917 #
1. yunohn ◴[21 Nov 24 16:27 UTC] No.42205917[source]▶
Why would you assume single digit extra calls? If the list is N million, then you would do a constant multiple of iterations of that. That’s a non trivial overhead in production applications.
replies(1): >>42211162 #
2. me-vs-cat ◴[22 Nov 24 04:21 UTC] No.42211162[source]▶
You're choosing the weakest strawman interpretation and ignoring the rest of what I said.

Bye, have fun!