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Python | Sort list containing alphanumeric values

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  • Last Updated : 19 Jul, 2019
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Given a list containing both alphanumeric values, write a Python program to sort the given list in such a way that the alphabetical values always comes after numeric values.

Examples:

Input : ['k', 5, 'e', 3, 'g', 7, 0, 't']
Output : [0, 3, 5, 7, 'e', 'g', 'k', 't']

Input : [1, 'c', 3, 2, 'a', 'b']
Output : [1, 2, 3, 'a', 'b', 'c']

Approach 1 : Using sort() method

To use Python sort() method we need to convert all list values to str type first. Now there are two methods to convert values to string.

  • Method #1 : List comprehension
    Python list comprehension can be simply used to convert each element of list to string type. We sort it and since all values are now str type, we change the final list to back to its original form.




    # Python3 program to Sort list 
    # containing alpha and numeric values
      
    def sort(lst):
        lst = [str(i) for i in lst]
        lst.sort()
        lst = [int(i) if i.isdigit() else i for i in lst ]
        return lst
                  
    # Driver code
    lst = ['k', 5, 'e', 3, 'g', 7, 0, 't']
    print(sort(lst))

    Output:

    [0, 3, 5, 7, 'e', 'g', 'k', 't']
    
  • Method #2 : Using key function

    Key function serves as a key for the sort comparison, which is equal to str in our case.




    # Python3 program to Sort list 
    # containing alpha and numeric values
    def sort(lst):
      
        lst.sort(key = str)
        return lst
      
    # Driver code
    lst = ['k', 5, 'e', 3, 'g', 7, 0, 't']
    print(sort(lst))

    Output:

    [0, 3, 5, 7, 'e', 'g', 'k', 't']
    

Approach 2 : sorted()

Alternatively, you can also use Python’s in-built function sorted() for the same purpose. Simplest difference between sort() and sorted() is: sort() doesn’t return any value while, sorted() returns an iterable list. Now there are again two ways of using sorted().

  • Method #1 : Using key function




    # Python3 program to Sort list 
    # containing alpha and numeric values
      
    def sort(lst):
      
        return sorted(lst, key = str)
                  
    # Driver code
    lst = ['k', 5, 'e', 3, 'g', 7, 0, 't']
    print(sort(lst))

    Output:

    [0, 3, 5, 7, 'e', 'g', 'k', 't']
    
  • Method #2 : lambda




    # Python3 program to Sort list 
    # containing alpha and numeric values
      
    def sort(lst):
          
        return sorted(lst, key = lambda x: (isinstance(x, str), x))
                  
    # Driver code
    lst = ['k', 5, 'e', 3, 'g', 7, 0, 't']
    print(sort(lst))

    Output:

    [0, 3, 5, 7, 'e', 'g', 'k', 't']
    

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