Lists

A Simple List

Besides numbers and text, variables can contain a collection of items called a list

• For example
  • a collection (list) of colors: colors = ['green', 'blue', 'red', 'yellow']
• Once we create a list, we can use it in a for loop as follows:

colors = ['green', 'blue', 'red', 'yellow']
for color in colors:
    jet.color(color)

    # Draw a square

• The full code can be found here: https://trinket.io/python/94de1feac8

What Else Can We Do With a List?

Let's start with a list: colors = ['green', 'blue', 'red', 'yellow']

Operation	Result
colors.append('green')	colors = ['green', 'blue', 'red', 'yellow“, 'green']
colors.insert(2, 'green')	colors = ['green', 'blue', 'green', 'red', 'yellow“, 'green']
colors.remove('green')	colors = ['blue', 'green', 'red', 'yellow“, 'green']
color = colors.pop(2)	color = 'red', colors = ['blue', 'green', 'yellow', 'green']
color = colors.pop()	color = 'green', colors = ['blue', 'green', 'yellow']
colors.sort()	colors = ['blue', 'green', 'yellow']
colors.reverse()	colors = ['yellow', 'green', 'blue']
colors.clear()	colors = []

Taking It a Step Further

• Find the number of elements in a list:

colors = ['green', 'blue', 'red', 'yellow']
number = len(colors)
print(number)

Challenge

1. Get a random number of colors from the user
   1. hint: color = input('Enter a color: ')
2. Store the color in a list of colors
3. Draw the polygons, one in each color, in a similar manner to the four squares.
   1. Let the number of sides of each polygon be equal to the number of colors that the user entered
      1. hint: # of sides = len(colors)
   2. Calculate the angle needed to draw a polygon
      1. hint: angle = 360 / # of sides
   3. Loop through all of the colors in the list you created
      1. hint:

         for color in colors:
             # set the color
             # begin fill
             # draw polygon
             # end fill
         # hide the turtle when done.
         

         

Need some help? Take a look here: https://trinket.io/python/06ab63c75f

What happens if the user only enters two colors? Can you add a check?