Get subset of list Python
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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: The code I have tried: for i in indx: if len(indx)==i: print(a[i:]) else: print(a[i:i+1])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: results = [a[indx[i]:indx[i+1]] for i in range(len(indx)-1)]
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: 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] |
