1 A shortcut for repeating code
In Lesson 2, drawing a square meant typing t.forward(100) and t.right(90) four times in a row.
Python has a shortcut for repeating code: a for loop.
for i in range(4):
t.forward(100)
t.right(90)
for i in range(4): repeats the two lines underneath it — 4 times.
2 Square with a loop — you fill it in
Fill in the two blanks to make a square, then click Run.
Hint:
A square has 4 sides.
A right-angle turn is 90°.
Still stuck? Tap here
Fill in: range(4) and right(90)
3 Triangle with a loop — you fill it in
Same idea, different shape. Fill in the blanks.
A triangle has 3 sides.
360° ÷ 3 = ?
Still stuck? Tap here
Fill in: range(3) and right(120)
4 Rectangle with a loop — you fill it in
A rectangle has 2 different side lengths, so the repeated block is bigger — but it repeats fewer times. Fill in the blanks.
A rectangle has 4 sides, but this loop’s block already has 2 sides in it (one long, one short).
How many times must the block repeat to make all 4 sides?
Still stuck? Tap here
Fill in: range(2) and forward(80)
5 Now you try: a pentagon
A pentagon has 5 equal sides. This time, there’s no code to copy — you need to work out the turn angle yourself before you write the loop.
A full turn all the way around is 360°.
A pentagon has 5 corners.
What calculation would tell you the turn angle at each corner?
Hint:
A loop for a shape with equal sides needs two things: how many times to repeat, and how far to turn.
Look back at the square and triangle loops if you get stuck.
Still stuck? Tap here
A pentagon has 5 sides. 360° ÷ 5 = 72°.
for i in range(5):
t.forward(100)
t.right(72)
What you learned in this lesson
for i in range(n):repeats the indented lines underneath it n times- loops let us draw a shape’s sides with far less code than typing each one out
- a shape with equal sides repeats a short block many times (like the square and triangle)
- a shape with unequal sides repeats a bigger block fewer times (like the rectangle)
- for a shape with n equal sides, turn 360° ÷ n at each corner