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Python programming

Python programming. Introduction to the JES environment and basics of Python. Python. The programming language we will be using is called Python http://www.python.org It’s used by companies like Google, Industrial Light & Magic, Nextel, and others

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Python programming

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  1. Python programming Introduction to the JES environment and basics of Python

  2. Python • The programming language we will be using is called Python • http://www.python.org • 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) • http://www.jython.org • 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:http://code.google.com/p/mediacomp-jes/

  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: >>> 5 + 3 8 >>> ‘spam’ ‘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 num = -3 • Floating point number 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 userOpens 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 2.1-2.4 from “Introduction to Computing and Programming in Python” (up to page 22)

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