Download Python and OpenSesame

Introduction to:
Python and OpenSesame
Python
• A high-level programming language
• It can do a lot of things
• We will use python in this course in the
context of in-line scripting for opensesame.
• For that, you need to know how to write basic
scripts.
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Intro to: Python and OpenSesame
Python
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From: XKCD comics
Intro to: Python and OpenSesame
Python Shell
Start -> python -> Python GUI (IDLE)
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Intro to: Python and OpenSesame
Python Shell
• An Interpreter:
– You write a line of code
– Python interprets it and executes it
• Try:
– 1+1 [addition]
– 5*2 [multiplication]
– ‘hello’ [string]
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Intro to: Python and OpenSesame
Python Basic (Data) Types
• INT (integer) – 2,3,0,15,100000
• FLOAT (floating point) – 2.0, 3.5, 0.12, 100.999
• STR (string) – ‘Hello’, ”to you all”, ‘1+1’, “11”
• Use type(…) to check:
–2
– 2.2
– ‘2.2’
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Intro to: Python and OpenSesame
Variables (assign value to variable)
• X = 1; Y = 2.0; Z1 = ‘Gevald’; Z2 = ‘avoi’
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Operations on variables? No problem:
X+Y [int+float = float]
X/Y [/ = devision, // = int devision]
Z1+X [int+str = error]
Z1 + Z2 [str+str = str]
Z1*3 [str*int = str (overloaded?!)]
Z2*Y [str*float = error]
Intro to: Python and OpenSesame
Variables (jumping from types)
>> x = 2.0; y = 3
>> int(x)
2
>> str(x)
‘2.0’
>> float(y)
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Intro to: Python and OpenSesame
Variables (pointing)
>> x = 1; y = 2
x
1 (memory location: 112125123)
y
2 (memory location: 112125125)
>> x = y; x is y?
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x
1 (memory location: 112125123)
y
2 (memory location: 112125125)
Intro to: Python and OpenSesame
Variables (pointing) - continue
>> y = 1
x
1 (memory location: 112125123)
y
2 (memory location: 112125125)
>> x is y ?
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Intro to: Python and OpenSesame
Functions - BASICS
String:
“Hello World”
INPUT
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print(“Hello World”)
BLACK BOX
Intro to: Python and OpenSesame
OUTPUT
Script!
A text file (.py) with python instructions for the
interpreter.
No more one liners!
In Python Shell:
File -> New File
In the new File:
File -> Save As.. -> example.py
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Intro to: Python and OpenSesame
Script!
Super text files!
Special language keywords are highlighted in
different colors.
Example
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Intro to: Python and OpenSesame
Your first Python program
In a new file (Call it first.py)
1. Create a program that saves the phrase:
‘hello world’ in a variable called phrase.
2. Use the print function to print the content of
phrase.
3. Execute your program
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Intro to: Python and OpenSesame
Back to functions
Recall: input -> blackbox -> output
Python comes with many built-in functions.
For more information, visit the official documentation:
https://docs.python.org/2/library/functions.html
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Intro to: Python and OpenSesame
Back to functions
Examples:
>> len() # returns the length of the input
>> abs() # returns the absolute value
>> round() # rounds to the nearest integer
>> raw_input() # takes user input as str
Notice I’m using # (hash
.mark) for comments.
Python ignore everything
after this symbol, but you
shouldn’t!
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Intro to: Python and OpenSesame
Python Standard Library
But the built-in functions are limited, and Python has
MUCH MORE to offer in the Python Standard Library
(https://docs.python.org/2/library/index.html)
The python standard library has many modules (script
files and folders) with many useful functions that are
readily available – once imported.
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Intro to: Python and OpenSesame
Python Standard Library - Modules
Math
>> import math
>> help(math) # lists all the available functions
The dot stands for
from, as in: use sin
from math
To use a function:
>> math.sin() # The sine function
>> math.factorial() # the factorial (‫ )עצרת‬function
(also has some special variable values like math.pi)
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Intro to: Python and OpenSesame
Python Standard Library - Modules
>> Import random
>> random.random()
if you only plan on using one function from a module:
>> from random import random
>> random()
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Intro to: Python and OpenSesame
More Python libraries
Python has even more libraries available on the web
which you could download and use.
We will not cover these in this class, but feel free to
explore:
numpy, matplotlib and more..
(Talk to me later if you want to learn more about this)
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Intro to: Python and OpenSesame
Objects – Tip of the iceberg!
Traditionally, this part comes much later in the learning process.
But, it is essential for OpenSesame scripts and I believe the tools
which it provides will help learning the other stuff.
Everything in Python is an object. This is what makes Python an
OOP [Object Oriented Programming] language.
What is an “OBJECT”?
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Intro to: Python and OpenSesame
Objects – Tip of the iceberg!
Objects are blueprints
Roof
Chimney
Door
Handle
Address
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Owner
# Rooms
Intro to: Python and OpenSesame
Color
Who lives
there?
Objects – Tip of the iceberg!
We can create an instance of an object:
>> house1 = house()
We can add properties to it:
>> house1.address = ‘Ragar 19, Be’er Sheva’
>> house1.price = 100000
>> house1.roof_color = ‘pink’
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Intro to: Python and OpenSesame
These Belong
EXCLUSIVELY to the
house1 instance of
the house object
Methods
• Objects have functions – called Methods
• Methods are functions that belong to the object
type.
Just an in object
variable
>> house.color
Pink
>> house.repaint(‘yellow’)
>> house.color
yellow
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Intro to: Python and OpenSesame
a method, notice the
parenthesis.
Methods
We said everything in Python is an object.
Int, float, str are objects too!
st = ‘stringy‘ # Creating a string instance
st.strip(‘y‘) # Using the strip method
Ask for help! Use help(str) to learn all the str methods
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Intro to: Python and OpenSesame
Importing new objects!
Similar to functions, we can import new objects
from the Python Standard Library.
We will now import the turtle library.
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Intro to: Python and OpenSesame
Turtle
Turtle is based on an old children’s programming
language called “Logo”.
we will use turtle throughout the course to
visualize everything we learn!
(This approach will also help us with OpenSesame
inline which uses objects all the time!)
** Some of the examples in this part were adopted from the Udacity Object Oriented Programming – Python course
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Intro to: Python and OpenSesame
Turtle – How it works
Move Forward, 100 steps
(0,0)
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Intro to: Python and OpenSesame
Turtle - setup
First, we need to import the turtle module which has all
the code for the needed objects.
** note: to make sure turtle works well, write all the
code in script files and NOT in the shell.
I still use >> to indicate that it’s a line of code.
>> import turtle
We will need two objects
1. A screen object
2. A turtle object
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Intro to: Python and OpenSesame
Turtle – Screen Object
>> import turtle
>> window = turtle.Screen()
We created a new Screen instance called window
Let’s use methods to change its appearance and behavior:
>> window.bgcolor(‘red’) # sets the background to red
>> window.exitonclick() # sets the close window properties
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Intro to: Python and OpenSesame
Turtle – Turtle Object
>> yoni = turtle.Turtle()
What can yoni (turtle instance) do?
>> yoni.forward(100) # Go forward, 100 steps!
>> yoni.right(10) # Turn right, 10o !
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Intro to: Python and OpenSesame
Time for a Python Program
In a new file (call it, square.py)
Use the turtle object to draw a square!
Don’t forget to create a window instance and use
the exitonclick() method in the end of the script
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Intro to: Python and OpenSesame
Another type, Bool (Boolean)
Use the type()
function to on the
input True
• Bool is a True/False type
• It is the basis of conditioning
• You get a Boolean value for these type of
statements:
– 1000 > 999
– ‘aaa’ == ‘bbb’
– 1 in (1,2,3,4)
– and more [ >=, <= , != ]
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Intro to: Python and OpenSesame
Conditionals
• Sets conditions to the program in the form:
Condition
if <this == True>:
<do that>
Indentation
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Intro to: Python and OpenSesame
Colon
Conditionals
• Example:
Where is the <True>
?
>> x = 5
>> y = 6
>> if x > y:
>> print(‘x is bigger than y’)
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Intro to: Python and OpenSesame
Conditionals – what else?
• We can create more advanced conditions:
if 1 > 2:
print(‘a new fact!’)
else:
print(‘The world is in order’)
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Intro to: Python and OpenSesame
Conditionals – what else?
• And even more advanced conditions:
if 1 > 2:
print(‘1 > 2’)
elif 2 > 1:
print(‘2 > 1’)
else:
print(‘Chaos!’)
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Intro to: Python and OpenSesame
Logical Operators (AND / OR)
x = 1; y = 2; z = 3
if x == 1 and y == 2:
print ‘ok’
if y == 2 or z == 4:
print ‘no worries’
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Intro to: Python and OpenSesame
Time for a Python Program
In a new file (call it, conditions.py)
Write a program that:
1. Sets x and y to be either 1 or 2 randomly.
2. If x is bigger than y, draw a square with turtle
3. If y is bigger than x, draw a circle with turtle
4. If x and y are equal, draw a line with turtle
Hint: Use the choice() function from the random module, it takes
as input a number sequence from which it draws a choice (1,2).
Also, turtle has a draw circle function, find out what it is.
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Intro to: Python and OpenSesame