1. Introduction to the JES environment and basics of Python
Python programming
Introduction to the JES environment and basics of Python
Do show this live – lots of examples, live installation.

2. Python The programming language we will be using is called Python
It’s used by companies like Google, Industrial Light & Magic, Nextel, and others
The kind of Python we’re using is called Jython (Java-based Python)
We’ll be using a specific tool to make Python programming easier, called JES (Jython Environment for Students).
JES 4.3 available as free download:
URL to look at what companies use Python is in the book.

3. JES - Jython Environment for Students
Program area
- A simple editor for
programs
Command area
Interaction with Jython

4. Python interaction through commands
Anything you type in command area is evaluated and its value is displayed
Example:
>>> 8
>>> ‘spam’
‘spam’
>>> “spam”
>>> “spam and more spam”
‘spam and more spam’
>>> ‘spam’ + ‘spam’
‘spamspam’
prompt

5. print displays the value of an expression
In many cases it makes no difference whether you use print - the result gets displayed anyway.
>>> print 5 + 3 8
>>> print ‘spam’
spam
>>> ‘spam’ + ‘spam’
‘spamspam’
>>> print ‘spam’ + ‘spam’
Spamspam
Note: no quotes!

6. Command Area Editing Up/down arrows walk through command history
You can edit the line at the bottom
Just put the cursor at the end of the line before hitting Return/Enter.

7. Variables are names for data
Example:
a= 3
b= -1
c = 2
x = 0
f = a*x*x + b*x + c

8. Variables -more examples
Variables of other types
newsItem = “You’ve got spam!”
Variables keep their value for the duration of a program or until they get a new value through a new assignment
a = 3
b = a *2 + 5
a = 0
Up to this point
the value of a is
still 3, but then
it changes to 0

9. Types of data Integer Floating point number Character String num = -3
answer = 62.49
Character
letter = ‘5’
String
note = “lol jkjk”

10. Python functions
Python has a lot of built-in functions for general mathematical manipulation, eg:
sqrt(4) - computes the square root of 4
ord(‘A’) - computes the ASCII code for character ‘A’ (i.e., a numeric code)
str(4) – produces a string corresponding to a number
Example:
print (-b+sqrt(b*b - 4*a*c))/2*a

11. Special JES-Python functions
JES defines some special functions for media computation

12. Functions in general 4
‘a’
F(a,b)
side-effects
F(4, ‘a’)

13. Example: sqrt() 4
sqrt(a)
side-effects 2

14. Example: showInformation()
showInformation(message): message: the message to show to the user Opens a message dialog to the user showing information
message
showInformation(message)
Pops up a new window
displaying the message text

15. Exploring more functions
The JES Functions menu has functions arranged by type - check them out!
Can you find a function that inputs a number?
Can you find under what category pickAFile() is listed?

16. Reading
Chapters 1, and Sections from “Introduction to Computing and Programming in Python” (up to page 22)