Feature: masked slicing

[arsserpentarium]

there is other quite similar feature suggestion,which is related to list indexing:
#156
However, I need a bit different thing. List indexing for bit retrieval:
`

a = bitarray('10010011')
lst = [1,0,1,0,1,1,1,1] #masking
a[lst]
bitarray('100011')
a[bitarray('10111000')]
bitarray('1101')
lst = [0,1,3,7] #indexing
a[lst]
bitarray('1011')
`

I'd be glad to see that functions in any implementation.

[ilanschnell]

Thanks for using bitarray! If I understand your example correctly, masking is simply the (already existing) & operator:

>>> a = bitarray('10010011')
>>> lst = [1,0,1,0,1,1,1,1] #masking
>>> a & bitarray(lst)  # you wrote a[lst] here
bitarray('10000011')

I'm having the same concerns as with #156 for adding the indexing with a list feature. So having bitarray.util.getitems() as well. If I get some time, I would implement both of these functions at once.

[arsserpentarium]

nope. And operator can't compose bitarray from bits of sequence a, which are on places of 1 in b. Numpy can do such thing, but it's quite inconvenient to use numpy for binary processing.

It'll be fine if that feature would be implemented as function.

thank you for your library.

[ilanschnell]

#204 has now been merged which allows indexing by lists

[ilanschnell]

#205 has been merged which can now allows indexing by bitarrays as masks, see:
https://github.com/ilanschnell/bitarray/blob/master/doc/indexing.rst#masked-indexing

[addandaum]

Oh thank you very much.

[ilanschnell]

The new features (sequence and masked indexing) are now available in bitarray 2.8.0