sub-list extraction, logical indexation

[Pierre]

Hello Everyone,

I would like to know if it is possible to extract a sub-list from a
list ?

typically if :

L =[[1, 2, 3],[4, 5, 6],[3] ]

How to extract easily the elements 0 and 2 of L in order to get :

L2 =[[1, 2, 3],[3] ]

Moreover, I would like to know if it is possible to use logical
indexation such that :

index = [ True, False, True]
L2 = L

or usual indexation, something like
index=[0, 2]
L2 = L

I tried, but failed...
Thanks for your help

Pierre

 

[Diez B. Roggisch]

Hello Everyone,

I would like to know if it is possible to extract a sub-list from a
list ?

typically if :

L =[[1, 2, 3],[4, 5, 6],[3] ]

How to extract easily the elements 0 and 2 of L in order to get :

L2 =[[1, 2, 3],[3] ]

Moreover, I would like to know if it is possible to use logical
indexation such that :

index = [ True, False, True]
L2 = L

or usual indexation, something like
index=[0, 2]
L2 = L

I tried, but failed...
Thanks for your help

index = [ True, False, True]
L2 = [v for i, v in enumerate(L) if index]

Diez

 

[MRAB]

Hello Everyone,

I would like to know if it is possible to extract a sub-list from a
list ?

typically if :

L =[[1, 2, 3],[4, 5, 6],[3] ]

How to extract easily the elements 0 and 2 of L in order to get :

L2 =[[1, 2, 3],[3] ]

Moreover, I would like to know if it is possible to use logical
indexation such that :

index = [ True, False, True]
L2 = L

or usual indexation, something like
index=[0, 2]
L2 = L

I tried, but failed...
Thanks for your help

index = [ True, False, True]
L2 = [v for i, v in enumerate(L) if index]

Or:

L =[[1, 2, 3],[4, 5, 6],[3] ]
index = [ True, False, True]

from itertools import izip
L2 = [v for i, v in izip(index, L) if i]

 

[Terry Reedy]

Hello Everyone,

I would like to know if it is possible to extract a sub-list from a
list ?

typically if :

L =[[1, 2, 3],[4, 5, 6],[3] ]

How to extract easily the elements 0 and 2 of L in order to get :

L2 =[[1, 2, 3],[3] ]

L2 = [L[0],L[2]]

Moreover, I would like to know if it is possible to use logical
indexation such that :

index = [ True, False, True]
L2 = L

use zip(index,L) in a for loop

or usual indexation, something like
index=[0, 2]
L2 = L

#untried
L2=[]
for i in index
L2.append(L)

tjr