how to get subset of list from index of list in python
I had a list of strings, I need to subset from the list based on their indexes list in generic manner
I need to get subsets in generic manner in first iteration:
a[0:5]2nd iteration:
a[5:7]3rd iteration:
a[7:]The code I have tried:
Expected output:
a[0:5]=='a', 'b', 3, 4, 'd' a[5:7]=6, 7 a[7:]=8You can try this :
indx.append[len[a]] print[*[a[i:j] for i,j in zip[indx, indx[1:]]], sep='\n']OUTPUT :
['a', 'b', 3, 4, 'd'] [6, 7] [8]Use a comprehension:
>>> [a[x:y] for x,y in zip[indx,[*indx[1:], None]]] [['a', 'b', 3, 4, 'd'], [6, 7], [8]]Will return a list containing the 3 lists you want.
You were right in thinking of iterating through two items at once, but the issue is that for i in lst does not use indexes, and will fail.
One way to iterate and take two items is by using zip.
Here you go.
for i in range[len[indx]]: try: print["a[%s:%s] ==" % [indx[i], indx[i + 1]] + " ", end=" "] print[a[indx[i]:indx[i + 1]]] except IndexError: print["a[%s:] ==" % [indx[i]] + " ", end=" "] print[a[indx[i]:]]Output:
a[0:5] == ['a', 'b', 3, 4, 'd'] a[5:7] == [6, 7] a[7:] == [8]You can use the slice type to convert your index list into list slices. As others have already posted, use zip to create the start-finish pairs:
>>> print[list[zip[indx, indx[1:]+[None]]]] [[0, 5], [5, 7], [7, None]]We use these pairs to define slices:
>>> slices = [slice[a, b] for a, b in zip[indx, indx[1:]+[None]]]Then use the slice object just like you would an integer index, but the slice will select the list substring as defined in the slice start-finish pair:
>>> for slc in slices: ... print[a[slc]]Gives:
['a', 'b', 3, 4, 'd'] [6, 7] [8]