Given the String list, write a Python program to compute sum of lengths of custom indices of list.
Examples:
Input : test_list = [“gfg”, “is”, “best”, “for”, “geeks”], idx_list = [0, 1, 4]
Output : 10
Explanation : 3 + 2 + 5 = 10. (Sizes of strings at idx.)
Input : test_list = [“gfg”, “is”, “best”, “for”, “geeks”], idx_list = [0, 2, 4]
Output : 12
Explanation : 3 + 4 + 5 = 12.
Method #1 : Using len() + loop
In this, we iterate for all indices and check if they occur in index list, if yes, increment frequency in summation counter.
Python3
# Python3 code to demonstrate working of # Length sum of custom indices Strings # Using len() + loop # initializing list test_list = ["gfg", "is", "best", "for", "geeks"] # printing original lists print("The original list is : " + str(test_list)) # initializing idx list idx_list = [0, 1, 4] res = 0for idx, ele in enumerate(test_list): # adding length if index in idx_list if idx in idx_list: res += len(ele) # printing result print("Computed Strings lengths sum : " + str(res)) |
The original list is : ['gfg', 'is', 'best', 'for', 'geeks'] Computed Strings lengths sum : 10
Method #2 : Using sum() + len() + list comprehension
In this, we perform task of performing summation using sum(), rest all the functionalities are performed as per above method, just as one-liner.
Python3
# Python3 code to demonstrate working of # Length sum of custom indices Strings # Using sum() + len() + list comprehension # initializing list test_list = ["gfg", "is", "best", "for", "geeks"] # printing original lists print("The original list is : " + str(test_list)) # initializing idx list idx_list = [0, 1, 4] # performing summation using sum() # len() used to get strings lengths res = sum([len(ele) for idx, ele in enumerate(test_list) if idx in idx_list]) # printing result print("Computed Strings lengths sum : " + str(res)) |
The original list is : ['gfg', 'is', 'best', 'for', 'geeks'] Computed Strings lengths sum : 10
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