Python | Ways to sum list of lists and return sum list
List is an important container and used almost in every code of day-day programming as well as web-development, more it is used, more is the requirement to master it and hence knowledge of its operations is necessary. Given a list of lists, the program to suppose to return the sum as final list.
Let’s see some of the methods to sum list of list and return list.
Method # 1: Using Naive method
# Python code to demonstrate # sum of list of list # using naive method # Declaring initial list of list L = [[1, 2, 3], [4, 5, 6], [7, 8, 9]] # Printing list of list print("Initial List - ", str(L)) # Using naive method res = list() for j in range(0, len(L[0])): tmp = 0 for i in range(0, len(L)): tmp = tmp + L[i][j] res.append(tmp) # printing result print("final list - ", str(res)) |
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Output:
Initial List - [[1, 2, 3], [4, 5, 6], [7, 8, 9]] final list - [12, 15, 18]
Method #2: Using numpy array
A numpy is a general-purpose array-processing package. It provides a high-performance multidimensional array object, and tools for working with these arrays.
# Pyhton code to demonstrate # sum of list of list # using numpy array functions import numpy as np # Declaring initial list of list List = np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]]) # Printing list of list print("Initial List - ", str(List)) # Using numpy sum res = np.sum(List, 0) # printing result print("final list - ", str(res)) |
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Output:
Initial List - [[1 2 3]
[4 5 6]
[7 8 9]]
final list - [12 15 18]
Method #3: Using zip() and list comprehension
# Pyhton code to demonstrate # sum of list of list using # zip and list comprehension # Declaring initial list of list List = [[1, 2, 3], [4, 5, 6], [7, 8, 9]] # Printing list of list print("Initial List - ", str(List)) # Using list comprehension res = [sum(i) for i in zip(*List)] # printing result print("final list - ", str(res)) |
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Output:
Initial List - [[1, 2, 3], [4, 5, 6], [7, 8, 9]] final list - [12, 15, 18]
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