Sorting Lists

Gotta' Sort'em All!

Selection Sort

What is Sorting?

Sorting: Any process of arranging items systematically.

  • Ascending
    • Alphabetical: A-Z
    • Numerical: 0-9
  • Descending
    • Reverse Alphabetical: Z-A
    • Reverse Numerical: 9-0

Sorting a List Temporarily

We can sort a list temporarily by using the sorted() function. The sorted function lets you temporarily sort the list but it doesn't affect the original list. 


            cars = ['bmw', 'audi', 'toyota', 'subaru']
            # Temporarily sort the cars in alphabetical order
            print(sorted(cars))
            # The original list is left untouched.
            print(cars)
        

            > ['audi', 'bmw', 'subaru', 'toyota']
            > ['bmw', 'audi', 'toyota', 'subaru']

Sorting a List Temporarily in Reverse Order

We can provide the argument reverse = True to the sorted() function to print the sorted list in reverse order Temporarily. 


            cars = ['bmw', 'audi', 'toyota', 'subaru']
            # Temporarily sort the cars in alphabetical order
            print(sorted(cars, reverse=True))
            # The original list is left untouched.
            print(cars)
        

            > ['toyota', 'subaru', 'bmw', 'audi']
            > ['bmw', 'audi', 'toyota', 'subaru']

Reversing the Order of the List

We can permanently reverse the order of a list. 


            cars = ['bmw', 'audi', 'toyota', 'subaru']
            cars.reverse()
            # The original list is permanently reversed
            print(cars)
        

            > ['subaru', 'toyota', 'audi', 'bmw']

Permanent Sorts

Python allows us to quickly sort a list in alphabetical order with the sort() method 


              cars = ['bmw', 'audi', 'toyota', 'subaru']
              # Sort the cars permanently in alphabetical order
              cars.sort()
              print(cars)
                    

              > ['audi', 'bmw', 'subaru', 'toyota']

Reverse Sorting a List Permanently

You can sort a list in reverse order by passing the argument of reverse=True into the sort method. 


            cars = ['bmw', 'audi', 'toyota', 'subaru']
            # Sort the cars in reverse alphabetical order
            cars.sort(reverse=True)
            print(cars)
        

            > ['toyota', 'subaru', 'bmw', 'audi']

Finding the Length of a List

We can find how long a list is by calling the len() function on a list. 


            cars = ['bmw', 'audi', 'toyota', 'subaru']
            # Print the length of the list.
            print(len(cars))
        

            > 4