Python | Multiply each element in a sublist by its index
Given a list of lists, the task is to multiply each element in a sublist by its index and return a summed list.
Given below are a few methods to solve the problem.
Method #1: Using Naive Method
# Python3 code to demonstrate # to multiply numbers with position # and add them to return num import numpy as np # initialising list ini_list = [[3, 4, 7], [ 6, 7, 8], [ 10, 7, 5], [ 11, 12, 13]] # printing initial_list print ("initial_list ", ini_list) res = [] # Using Naive Method for sub_list in ini_list: sublistsum = 0 for i, value in enumerate(sub_list): sublistsum = sublistsum + i * value res.append(sublistsum) # printing result print ("result", res) |
Output:
initial_list [[3, 4, 7], [6, 7, 8], [10, 7, 5], [11, 12, 13]] result [18, 23, 17, 38]
Method #2: Using List comprehension
# Python3 code to demonstrate # to multiply numbers with position # and add them to return num # initialising list ini_list = [[3, 4, 7], [ 6, 7, 8], [ 10, 7, 5], [ 11, 12, 13]] # printing initial_list print ("initial_list ", ini_list) # Using list comprehension res = [sum(i * j for i, j in enumerate(sublist)) for sublist in ini_list] # printing result print ("result", res) |
Output:
initial_list [[3, 4, 7], [6, 7, 8], [10, 7, 5], [11, 12, 13]] result [18, 23, 17, 38]
Method #3: Using numpy
# Python3 code to demonstrate # to multiply numbers with position # and add them to return num import numpy as np # initialising list ini_list = [[3, 4, 7], [ 6, 7, 8], [ 10, 7, 5], [ 11, 12, 13]] # printing initial_list print ("initial_list ", ini_list) # Using numpy res = [np.arange(len(sublist)).dot(sublist) for sublist in ini_list] # printing result print ("result", res) |
Output:
initial_list [[3, 4, 7], [6, 7, 8], [10, 7, 5], [11, 12, 13]] result [18, 23, 17, 38]
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