Python: Sort the numbers by the sum of their digits

Python Programming Puzzles: Exercise-38 with Solution

Write a Python program to sort the numbers in a given list by the sum of their digits.

Input: 
[10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20] 
Output:
[10, 11, 20, 12, 13, 14, 15, 16, 17, 18, 19]

Input: 
[23, 2, 9, 34, 8, 9, 10, 74] 
Output:
[10, 2, 23, 34, 8, 9, 9, 74]

Pictorial Presentation:

Sample Solution-1:

Python Code:

#License: https://bit.ly/3oLErEI

def test(nums):
     return sorted(nums, key=lambda n: sum(int(c) for c in str(n) if c != "-"))
 
nums = [10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]
print("Original list of numbers:",nums)
print("Sort the numbers of the said list by the sum of their digits:")
print(test(nums))
nums = [23,2,9,34,8,9,10,74]
print("\nOriginal list of numbers:",nums)
print("Sort the numbers of the said list by the sum of their digits:")
print(test(nums))

Sample Output:

Original list of numbers: [10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]
Sort the numbers of the said list by the sum of their digits:
[10, 11, 20, 12, 13, 14, 15, 16, 17, 18, 19]

Original list of numbers: [23, 2, 9, 34, 8, 9, 10, 74]
Sort the numbers of the said list by the sum of their digits:
[10, 2, 23, 34, 8, 9, 9, 74]

Flowchart:

Sample Solution-2:

Python Code:

#License: https://bit.ly/3oLErEI

def test(nums):
    unordered = nums.copy()
    ordered = []
    while unordered:
        # The number that comes first, since the list is sorted by the primes
        smallest = unordered[0]
        s = sum(int(c) for c in str(smallest) if c != "-")
        for t in unordered:
            t_s = sum(int(c) for c in str(t) if c != "-")
            if t_s < s:
                smallest = t
                s = t_s
        ordered.append(smallest)
        unordered.remove(smallest)
    return ordered
 
nums = [10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]
print("Original list of numbers:",nums)
print("Sort the numbers of the said list by the sum of their digits:")
print(test(nums))
nums = [23,2,9,34,8,9,10,74]
print("\nOriginal list of numbers:",nums)
print("Sort the numbers of the said list by the sum of their digits:")
print(test(nums))

Sample Output:

Original list of numbers: [10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]
Sort the numbers of the said list by the sum of their digits:
[10, 11, 20, 12, 13, 14, 15, 16, 17, 18, 19]

Original list of numbers: [23, 2, 9, 34, 8, 9, 10, 74]
Sort the numbers of the said list by the sum of their digits:
[10, 2, 23, 34, 8, 9, 9, 74]

Flowchart:

Python Code Editor :

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