Pythonic way to get some rows of a matrix
I was thinking about a code that I wrote a few years ago in Python, at some point it had to get just some elements, by index, of a list of lists.
I remember I did something like this:
def getRows(m, row_indices): tmp =  for i in row_indices: tmp.append(m[i]) return tmp
Now that I've learnt a little bit more since then, I'd use a list comprehension like this:
[m[i] for i in row_indices]
But I'm still wondering if there's an even more pythonic way to do it. Any ideas?
I would like to know also alternatives with numpy o any other array libraries.
Asked by: Connie801 | Posted: 06-12-2021
It's worth looking at NumPy for its slicing syntax. Scroll down in the linked page until you get to "Indexing, Slicing and Iterating".Answered by: John317 | Posted: 07-01-2022
It's the clean an obvious way. So, I'd say it doesn't get more Pythonic than that.Answered by: Lenny392 | Posted: 07-01-2022
As Curt said, it seems that Numpy is a good tool for this. Here's an example,
from numpy import * a = arange(16).reshape((4,4)) b = a[:, [1,2]] c = a[[1,2], :] print a print b print c
Answered by: Byron204 | Posted: 07-01-2022
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