An Introduction to Python

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An Introduction to Python
Suzanne Dunford Mackenzie High School

• RCDSB Conference 2007
• Used and modified with the permission of Michael
  DiRamio NDSB

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This Session

• Differentiated Instruction in the Computer class
• Python Part 1
• Character education and computers yes!
• Python Part 2
• Assessment and Evaluation discussion
• Python - Summary

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Differentiated Instruction in the Computer class

• How does a computer class lend itself to this
  form of instruction?

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The use of Differentiated Instruction in ICS3M
and ICS4M

• Computer science classrooms lend themselves to
  differentiated learning
• Four ways to differentiate Instruction
• Content/Topic
• Process/Activities
• Product
• Individual Learning Styles

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Python Part 1
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Summary - Python Part 1

• Why Python?
• Textbooks
• Documentation in Python
• IDLE a Python IDE
• Activity 1
• Output
• Activity 2
• Arithmetic
• Activity 3

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Why Python?

• Why Python, not JAVA, C?
• UofT makes a choice
• Python is an interpreted language.

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Textbook choice

• Python Programming Second Edition for the
  absolute beginner by Michael Dawson
• published by Thomson ISBN 1-59863-112-8

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IDLE A Python IDE

• Free IDE download at www.python.org
• Has both interactive window and program files
  (script mode)

Interactions Window
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IDLE Interaction

• Allows you to try out an expression with
  immediate results.
• Output is the result of the expression

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Script Mode

• Why script mode?
• Just choose new program from File

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Most Important Feature in a Language
Documentation

• The symbol to start documentation in Python is

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How do we end the program?

• raw input (\n\n\Press the enter key to exit.)

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Activity 1 Exploration of IDLE and Script Mode

• Purpose to play with the interactions window,
  see what the results are.
• For the next 5 minutes try printing in IDLE
  (print Hello World) for example.
• Also, try out the comment symbol and the last
  command
• Textbook reference pages 11-14

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IDLE Writing Programs

• Programs can be written in files, saved, and run.
• The results are produced in the interactions
  window.

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Output

• The output keyword in Python is print. print
  will output anything, Strings, numbers, etc.
• Note the difference between simply putting
  Hello in the interactions window, and putting
  print Hello

gtgtgt 10 Hello
print 4 6 print "Hello"
program
output
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Activity 2 First Program

• Write a program (not in the interactions window,
  in a separate file) that outputs the famous
  quotation To be or not to be on the screen.
• Run this program (Run -gt Run Module) and see the
  output produced in the interactions window
• Reference in text book pages 17-24

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Concatenation

• String concatenation is the symbol

gtgtgt 'Hello ' 'World' 'Hello World'
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or ?

• Python allows you to use either single or double
  quotes for Strings.
• This prevents needing special characters if you
  want to use a quotation in your string.

gtgtgt print 'This contains "double quotes"' This
contains "double quotes" gtgtgt print "And here are
'single quotes' inside" And here are 'single
quotes' inside
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Math

• Uses standard arithmetic operations , -, /, ,
  (remainder)
• Note if you divide two integers, the result will
  be an integer
• More math functions like ceiling and floor are in
  the math module (not covered in this session)

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Activity 3 Division

• Explore the difference between
• 5 / 2
• and
• 5.0 / 2
• Textbook Reference pages 25-32

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Character Education in Programming class

• Honesty
• Perseverance
• Diligence

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Python Part 2
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Summary Python Part 2

• Variables
• Input
• Activity 4
• Looping
• Activity 5
• Selection
• Activity 6

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Variables

• Python variables dont carry type.

gtgtgt x 6 gtgtgt print x 3 9 gtgtgt x "Hello" gtgtgt
print x Hello gtgtgt print x " world" Hello world
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Input

• The method raw_input(string) returns a string the
  user has typed in
• The parameter to raw_input is the prompt given to
  the user.

x raw_input("ltTYPE SOMETHINGgt") print "The user
typed " x
Program
gtgtgt ltTYPE SOMETHINGgtThis is my input The user
typed This is my input
Output
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Input cont

• The string input can be converted to other types
  using conversion methods like int(string) and
  float(string)

x raw_input("ltTYPE A NUMBERgt ") y
int(x) print y 2
Program
gtgtgt ltTYPE A NUMBERgt 11 22
Output
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Activity 4 Input Conversion

• Write a program that reads in a temperature in
  Fahrenheit and converts it to Celsius
• C (F - 32) 5 / 9
• Textbook reference32-46

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Indentation

• Python doesnt use brackets to define blocks of
  code
• Indentation tells the program where a section
  ends
• If a program isnt properly indented you will get
  an error

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Loops
gtgtgt 0 1 2 3 4 5 6 7 8 9 done!
i 0 while i lt 10 print i i i
1 print "done!"

• The loop continues iterating as long as the
  condition following while remains true

Program
Output
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Activity 5 Importance of Indentation

• Create a program that uses a loop, like the
  previous example.
• Now remove the indentation and try running the
  program
• Textbook reference51-58

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Comparisions

• is used for equality testing
• Inequality is !
• Inequalities are straight forward lt, gt, lt, gt

gtgtgt print 8 lt 15 True gtgtgt print 9 ! 7 True
Interactions Window
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Selection Statements

• if/elif/else
• Must have one if clause
• Followed by 0 or more elif (else if) clauses
• Followed by 0 or 1 else clause

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Selection Statements Example

• Notice what happens when you remove the
  indentation.

x raw_input("input please") x int(x) if x lt
10 print "Small" elif x lt 20 print
"Medium" elif x lt 30 print "Big" else
print "HUGE!" print "Done"
gtgtgt input please21 Big Done
Program
Output
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Activity 6 Selection

• Write a program that reads in a number and
  determines if that number is even or odd.
• Textbook reference page 59 65

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Assessment and Evaluation

• Using same principles of honesty, perseverance
  and diligence in our assessment and evaluation
• Group discussion

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Summary of Python
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Use in Computer Programming

• Free IDE
• The interactions window allows students to
  quickly test out ideas.
• Lack of brackets keeps code uncluttered.
• Students must indent their code properly or it
  wont function properly.
• Lightweight syntax prevents students from
  becoming lost in the picky details of a language.

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Thanks again to Michael DiRamio.

• Plug Michael is giving a talk at the ACSE
  conference Nov. 10 on a different topic.