CPSC120B - Day 8 Notes

We already know how to use modules, we’ve been using them since the first Python program you created
When you add import turtle to the top of a file it allows you to use functions that begin with turtle dot something
It allows you to use code that someone else wrote
One useful module is the math module, which gives you functions like math.sin, math.cos, math.log
In addition to functions, modules can have variable you can use
The math module has math.pi so you don’t have create a constant
Another useful module is the random module, which give you functions to generate pseudo-random numbers
The random.random function gives random numbers in the range [0.0, 1.0) (note that is exclusive of 1.0)
The random.randrange function give random integers in the specified range (note the upper bound is exclusive)
The probablity distribution of both random functions is flat
What if you want to create a floating point number in a range?

So far we have created graphical programs using turtle
But turtle isn’t very good for creating animations
The underlying graphical system that turtle is built on is difficult to use
So I created a module to make creating animations easier
Using module that is not built-in requires an extra step
Before importing it, you have to put the module’s .py file in the same directory and the .py file that is using it.
The graphics module’s documentation has a link to the graphics.py file you can use during lab
To draw an oval use the draw_oval function, need to specify the x, y, width, and height
```
import graphics
graphics.draw_oval(0, 0, 100, 100)
```
Note the coordinate system is different than turtle, (0, 0) is in the upper left and positive y is down

Can also change the outline, fill, and thickness

import graphics
graphics.draw_oval(100, 100, 100, 200, 'red', 'blue', 5)

To create an animation, need to draw multiple times

import graphics
for i in range(100)
    graphics.draw_oval(i, i, 100, 100)

To add a delay, use the wait function

import graphics
for i in range(100)
    graphics.draw_oval(i, i, 100, 100)
    graphics.wait()

To remove the trail, need to clear the screen

import graphics
for i in range(100)
    graphics.clear()
    graphics.draw_oval(i, i, 100, 100)
    graphics.wait()

CPSC120B
Fundamentals of Computer Science