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Python | Sum of number digits in List
• Difficulty Level : Medium
• Last Updated : 01 Mar, 2020

The problem of finding summation of digit of number is quite common. This can sometimes come in form of list and we need to perform that. This has application in many domains such as school programming and web development. Let’s discuss certain ways in which this problem can be solved.

Method #1 : Using loop + `str()`
This is brute force method to perform this particular task. In this, we run a loop for each element, convert each digit to string and perform the count of sum of each digits.

 `# Python3 code to demonstrate ``# Sum of number digits in List``# using loop + str()`` ` `# Initializing list``test_list ``=` `[``12``, ``67``, ``98``, ``34``]`` ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `# Sum of number digits in List``# using loop + str()``res ``=` `[]``for` `ele ``in` `test_list:``    ``sum` `=` `0``    ``for` `digit ``in` `str``(ele):``        ``sum` `+``=` `int``(digit)``    ``res.append(``sum``)``     ` `# printing result ``print` `(``"List Integer Summation : "` `+` `str``(res))`
Output :
```The original list is : [12, 67, 98, 34]
List Integer Summation : [3, 13, 17, 7]
```

Method #2 : Using `sum()` + list comprehension
This task can also be performed using shorthand using above functionalities. The sum() is used to compute summation and list comprehension is used to compute iterations.

 `# Python3 code to demonstrate ``# Sum of number digits in List``# using sum() + list comprehension`` ` `# Initializing list``test_list ``=` `[``12``, ``67``, ``98``, ``34``]`` ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `# Sum of number digits in List``# using sum() + list comprehension``res ``=` `list``(``map``(``lambda` `ele: ``sum``(``int``(sub) ``for` `sub ``in` `str``(ele)), test_list))``     ` `# printing result ``print` `(``"List Integer Summation : "` `+` `str``(res))`
Output :
```The original list is : [12, 67, 98, 34]
List Integer Summation : [3, 13, 17, 7]
```

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