CODEWITHSUNDEEP
arrayspython-3.x
Titus
Titus

Reputation: 244

Shorter way to index array

I have a 2D array called my_array. To select the 1st, 13th, 14th, 15th, and the 16th element from each row I use the following line

desired_elements = my_array[:,[0,12,13,14,15]]

This works, but I'm pretty sure that the [0,12,13,14,15] part can be written more compactly. I have tried to look for a way, but until now I have been unable to do so.

Question: Is there a shorter way to write 

desired_elements = my_array[:,[0,12,13,14,15]]

Upvotes: 1

Views: 59

Answers (1)

bglbrt
bglbrt

Reputation: 2098

This is not shorter but equal in length for your specific input, but perhaps it is what you're looking for. You could be using np.r_, which translates slice objects to concatenation along the first axis.

It's a simple way to build up arrays quickly when you have multiple slices to select.

Here's how you would do with your example:

desired_elements = my_array[:, np.r_[0, 12:16]]

Now, if you wanted to select more slices, you would probably end up with something shorter than the approach you take, for instance:

desired_elements = my_array[:, np.r_[0, 4:8, 11:14]]

May I ask why it is so critical to shorten your input?

Upvotes: 1

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