4.7 The range Function

• When called with one parameter, the sequence provided by rangealways starts with 0
• If you ask for range(4), then you will get 4 values starting with 0
  • 0, 1, 2, and finally 3
  • 4 is not included since we started with 0

for i in range(4):
    # Executes the body with i = 0, then 1, then 2, then 3
for x in range(10):
    # sets x to each of ... [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

for i in range(4):
    alex.forward(50)
    alex.left(90)

Two parameter Range

• The evaluation of range(1,5) produces the desired sequence of 1-4
• we interpret the parameters of the range function to mean range(start,beyondLast)
  • beyondLast means an index past the last index we want: 4+1

Three Parameter Ranges

• Third parameter: step
• Tells the range what to count by
• So if we wanted the first 10 even numbers we would use range(0,19,2)
• The most general form of the range is range(start, beyondLast, step)
• You can also create a sequence of numbers that starts big and gets smaller by using a negative value for the step parameter.

print(list(range(0, 19, 2)))
print(list(range(0, 20, 2)))
print(list(range(10, 0, -1)))