Last time in Python class

1. Interpreter in the terminal
2. Interpreter in IDLE
3. Interpreter via files
4. Types
   1. string
   2. int
   3. float

Functions

A function is a piece of code that's already written

It can be called whenever you want

Functions look like this:

function_name(list_of_parameters_separated_by_comma)

Example: len("I like my dog")

pow(2,8)

print

print is a function, but it's an exception

in Python 3, it's no longer an exception, they fixed it

for now we use: print "I like my dog"

import

Many functions are defined in libraries

You have to import the library before you can access the function

import math
math.sqrt(16)

The TURTLE

Yes, I said turtle

Try the following

1. import the module called "turtle"
2. create a turtle
3. ask Python to tell us what exactly did we create

import turtle         
t = turtle.Turtle()   
print type(t)        

What is the type of the variable t?

<class 'turtle.Turtle'>

A class is an object.

strings, integers and floats are all objects.

We just created a turtle object

Just like strings have some internal behaviour that we can use, turtles have fun behaviours

Remember
"the lord of the rings".title()

All calls to objects will follow this pattern:
object dot functionName parenthesis

Let's get our turtle moving!

import turtle
beach = turtle.Screen()
t = turtle.Turtle()
t.forward(150)
turtle.done()

Let's go over the code and see what each one does

• import turtle
• beach = turtle.Screen()
• t = turtle.Turtle()
• t.forward(150)
• turtle.done()

Some fun

Try: (add it before the forward call)

Other shapes are “arrow”, “circle”, “square”, “triangle”, “classic”

Some fun part 2

Try:

It's the same as t.hideturtle()
Now it makes sense! ht -> hideturtle

And get your turtle back with t.showturtle() or t.st()

More fun

Try: (before the call to forward() fd() )

Try different colours

Hexa colors like #F0F0F0

RGB codes, like (255,0,255)

Gimme a red square

you might want to use the following:

• .forward(distance)
• .left(degrees)

import turtle
beach = turtle.Screen()
beach.title("RED SQUARE")
t = turtle.Turtle()
t.pencolor("red")
t.forward(200)
t.right(90) 
t.forward(200)
t.right(90)
t.forward(200)
t.right(90)
t.forward(200)
t.right(90)     
beach.exitonclick()

Let's put the square in the center

Think about the width and height of the square

t.goto(-100,100)

Let's remove that extra line

t.penup() 

t.pendown()

DRY : DON'T REPEAT YOURSELF

all those forwards and turn right are annoying

for i in range(4):
    t.forward(200)
    t.right(90)

Woah! Lots of things here!

for i in range(4):

a range is an enumeration.

it's the difference between 4 and counting up to 4 (1,2,3,4)

So range(4) means 0,1,2,3

for i in range(4):

i is the name of a variable.

for i in range(4):

basically tells the computer to count up to 4

anything that is in the block following it is executed each time

a block starts after the colon

every line must be indented perfectly

BLOCKS

many bugs can be blamed on wrong indentation

be warned!

Here is the block again

for i in range(4):
   t.forward(200)
   t.right(90)

Blocks are the legos of Python

Always the same format:

• One line of logic reasoning, ended with a colon
• one or more lines of INDENTED python code (4 spaces)

let's modify our for loop slightly

for i in range(8):
   t.forward(200)
   t.right(225)

Here's the result:

let's modify our for loop slightly more

this will take a bit long, so we add a line before the loop

t.speed(0)
for i in range(37):
   t.forward(200)
   t.right(175)

Another result:

a last one

for i in range(20):
    t.forward(100)
    t.left(94.65)

What do you get if we do this change?

for i in range(4):
    t.forward(200)
    for j in range(12):
        t.left(30)
        t.fd(5)
    t.right(90)

Here's what you're supposed to get

So a block can be part of another block, as we just saw

blocks are like...

Let's do a star

for x in range(1,19):
   t.forward(100)
   if x % 2 == 0:
      t.left(175)
   else:
      t.left(225)