Python | Variable list slicing
The problem of slicing a list has been dealt earlier, but sometimes we need to perform the slicing in variable lengths according to the input given in other list. This problem has its potential application in web development. Let’s discuss certain ways in which this can be done.
Method #1 : Using itertools.islice() + list comprehension
The list comprehension can be used to iterate through the list and the component issue is solved using the islice function.
# Python3 code to demonstrate # variable length slicing # using itertools.islice() + list comprehension from itertools import islice # initializing test list test_list = [1, 5, 3, 7, 8, 10, 11, 16, 9, 12] # initializing slice list slice_list = [2, 1, 3, 4] # printing original list print("The original list : " + str(test_list)) # printing slice list print("The slice list : " + str(slice_list)) # using itertools.islice() + list comprehension # variable length slicing temp = iter(test_list) res = [list(islice(temp, part)) for part in slice_list] # print result print("The variable sliced list is : " + str(res)) |
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Output :
The original list : [1, 5, 3, 7, 8, 10, 11, 16, 9, 12] The slice list : [2, 1, 3, 4] The variable sliced list is : [[1, 5], [3], [7, 8, 10], [11, 16, 9, 12]]
Method #2 : Using zip() + accumulate() + list slicing
Apart from using the list comprehension to perform the task of binding, this method uses zip function to hold sublist element together, accumulate function joins the elements, and slicing is used to construct the required slicing.
# Python3 code to demonstrate # variable length slicing # using zip() + accumulate() + list slicing from itertools import accumulate # initializing test list test_list = [1, 5, 3, 7, 8, 10, 11, 16, 9, 12] # initializing slice list slice_list = [2, 1, 3, 4] # printing original list print("The original list : " + str(test_list)) # printing slice list print("The slice list : " + str(slice_list)) # using zip() + accumulate() + list slicing # variable length slicing res = [test_list[i - j: i] for i, j in zip(accumulate(slice_list), slice_list)] # print result print("The variable sliced list is : " + str(res)) |
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Output :
The original list : [1, 5, 3, 7, 8, 10, 11, 16, 9, 12] The slice list : [2, 1, 3, 4] The variable sliced list is : [[1, 5], [3], [7, 8, 10], [11, 16, 9, 12]]
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