Week 5: Python Variable Snowflakes

Review

• For loops
• Variables
• Random integers
• Angles of rotation

Discussion

• Functions
• A block of organized, reusable code that is used to perform a certain action
• User-defined functions: written by the programmer
• Avoid re-writing multiple lines of code (for tasks you want to perform more than once)
• Define code to perform some action within a function, and use a command to call that function every time you want that action to run.
• Pass in function parameters to create flexible programs
• Create varying outputs depending on values passed in
• i.e. Snowflakes with various colours and shapes, by passing in different values for colours and lengths.

• Variables that change over time
  • Have many inputs without having to provide them manually

Lesson & Practice

1a. Snowflake (user-defined function)

1b. Shapes using user-defined functions with parameters

def snowflake(): size = 10 for count in range(size): t.color(random.randint(0, 255), random.randint(0, 255), random.randint(0, 255)) t.forward(50) t.stamp() t.backward(20) t.left(45) t.forward(20) t.backward(20) t.right(90) t.forward(20) t.backward(20) t.left(45) t.backward(30) t.left(360/size) return
function call: snowflake()

def snowflake_parameters(length, number_of_rays, colour): for count in range(number_of_rays): t.color(colour) t.forward(length) t.stamp() t.backward(length/3) t.left(45) t.forward(length/3) t.backward(length/3) t.right(90) t.forward(length/3) t.backward(length/3) t.left(45) t.backward(length*(2/3)) t.left(360/number_of_rays) return t.penup() t.goto(0, -100) t.pendown() for count in range (5): snowflake3(40, 10, “blue”) t.penup() t.goto(random.randint(-100, 100), random.randint(-100, 100)) t.pendown() snowflake3(15, 6, “violet”) t.penup()

t.goto(random.randint(-100, 100), random.randint(-100, 100)) t.pendown()

2. Variables that change over time (Snowflakes with varying RGB)