Related Articles
Python – Find the sum of Length of Strings at given indices
• Last Updated : 02 Dec, 2020

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 ``=` `0``for` `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))`
Output
```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))`
Output
```The original list is : ['gfg', 'is', 'best', 'for', 'geeks']
Computed Strings lengths sum : 10```

Attention geek! Strengthen your foundations with the Python Programming Foundation Course and learn the basics.

To begin with, your interview preparations Enhance your Data Structures concepts with the Python DS Course. And to begin with your Machine Learning Journey, join the Machine Learning – Basic Level Course

My Personal Notes arrow_drop_up