Loops: The Lazy Way to Draw

Welcome to Week 2! Last week, drawing a hexagon meant typing forward and right six times each — twelve lines for one shape. Good programmers hate repeating themselves. Today you learn the single most useful idea in all of programming: the loop.

Tell Python to repeat

A loop says “do this, a bunch of times.” Here’s the shape of it:

for step in range(4):
    # the indented lines happen 4 times

Two things to notice:

  • range(4) means do it 4 times.
  • The repeated lines are indented (pushed in). The indentation is how Python knows what’s “inside” the loop.

Here’s a whole square. The two lines you used to repeat are now written once, inside a loop:

 
 
  

Same square. The dozen lines became two. That’s the magic: write it once, tell Python how many times.


Try it 🎯


    

  1. Change range(4) to range(3) and right(90) to right(120). A triangle!
    2. 

  2. Change to range(5) and right(72). A pentagon!
    3. 

  3. Change forward(100) to forward(160). Bigger.
    4. 



The shape rule, now with loops


Remember the rule from Lesson 2? Turn = 360 ÷ number of sides. A loop makes it effortless — you only change two numbers: the count in range(...) and the turn.





































Shaperangeturn
Triangle3120
Square490
Pentagon572
Hexagon660
Octagon845


Your turn 🎯


Make a hexagon (6 sides). Change the range number and the turn to match the table:


   
   
 
 
 
 
 
  

Predict it 🔮


Using the table: what shape does range(8) with right(45) make? Guess first, then Run:


   
   
 
 
 
 
 
  

(An octagon — 8 sides, like a stop sign.)


Fix the bug 🐞


This loop is supposed to draw a triangle, but it makes a weird open shape. The range is right for a triangle, but the turn is wrong. Fix it using the rule:


   
   
 
 
 
 
 
  

(Three sides need a turn of 360 ÷ 3 = 120. Change right(90) to right(120).)


Sneaking up on a circle


What if you use lots of sides with tiny turns? Try 36 little steps, turning just 10 each:


   
   
 
 
 
 
 
  

Almost a perfect circle! A circle is really just a shape with so many tiny sides you can’t see the corners. (36 turns of 10 = 360, a full spin.)


Mix it up 🎨


In the near-circle above, try range(60) with t.right(6) (even smoother), or range(18) with t.right(20) (chunkier). What’s the smallest number of sides that still looks round to you?


Your mission 🚀


Draw a many-sided shape of your choice — anything from a triangle to a 12-sided shape. Pick your number of sides, use the rule (360 ÷ sides) for the turn, and set it up in a loop:


   
   
 
 
 
 
 
  

What you learned today


    

  • A for ... in range(n): loop repeats the indented lines n times.
    • 

  • Indentation marks what’s inside the loop.
    • 

  • Any equal-sided shape: count in range, turn = 360 ÷ sides.
    • 

  • Many tiny sides make a circle.
    • 



Loops don’t just save typing — they make brand-new things possible. Next time you’ll spin loops into spirals, stars, and flower-like patterns that would be almost impossible to type by hand. 🐢
   
 
 
 
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