Numerical Lists

The range() function

The range() function allows us to generate sequences of numbers with the following syntax:

Here is a simple program that prints out the numbers 1 through 4 to the console. Note that last number printed is less than the stop number.

                
                    # Range function with a the default step-size of 1
                    for value in range(1,5):
                        print(value)
                
                

                    1
                    2
                    3
                    4
                

It is also possible to specify a step-size by supplying a third argument:

                    # Print all even numbers from 1-10
                    for value in range(1,11,2):
                      print(value)
                  

                    1
                    3
                    5
                    7
                    9
                  

The list() Function

You can also make a range of numbers into a list by calling the list() function. You can then use any of the list methods such as sort() to manipulate your list.

            # Make a list of numbers from 1-4
            numbers = list(range(1,5))
                print(numbers)
            

              [1, 2, 3, 4]
            

Generating Custom Sequences

You are not just limited to counting by an integer step-size. You can specify an expression to generate almost any sequences imaginable:

              # Create an empty list
              squares = []
              # For loop to generate integers from 1 to 10
              for value in range(1,11):
              # Append the square of the integer in value to the List
                squares.append(value**2)
              # Print the list
              print(squares)
            

              [1, 4, 9, 16, 25, 36, 49, 64, 81, 100]
            

Simple Stats with Number Lists

You can use the min(), max() and sum() functions to get the minimum, maximum and sum of all the numbers in a list respectively

          digits = [1,2,3,4,5,6,7,8,9,0]
          # Find minimum, maximum and total sum of the digits list
          print(min(digits))
          print(max(digits))
          print(sum(digits))
        

          0
          9
          45
        

List Comprehensions

In a previous program, it took 3 lines to create a list of perfect square numbers but with a list comprehension you can do all three steps in one line.

        # Build a list of the first 10 perfect square numbers
        squares = [value**2 for value in range(1,11)]
        print(squares)
        

          [1, 4, 9, 16, 25, 36, 49, 64, 81, 100]