Python Introduction

1. Python Introduction Professor Frank J. Rinaldo Creation Core - office 401

2. Python • Textbook • Python Programming for the Absolute Beginner (2nd Edition) • By Michael Dawson • Premier Books • 2007 • ISBN: 1-59299-073-8

3. IDLE Integrated Development Environment • Interactive Mode • Type in code • Immediately executed • Useful for quick learning or debugging

4. IDLE Integrated Development Environment • Script Mode • Acts like a ‘usual’ editor • Type in multiple lines of code • Then ‘save’ the program • Then ‘run’ program

5. 1st Program # Game Over # Demonstrates the print command # Michael Dawson - 12/26/02 print "Game Over" raw_input("\n\nPress the enter key to exit.")

6. 2nd Program # Game Over - Version 2 # Demonstrates the use of quotes in strings # Michael Dawson - 1/9/03 print "Program 'Game Over' 2.0" #NOTE using ‘/’ to continue a line AND triple quoted double quotes “”” below print \ """ _____ ___ ___ ___ _____ / ___| / | / |/ | | ___| | | / /| | / /| /| | | |__ | | _ / ___ | / / |__/ | | | __| | |_| | / / | | / / | | | |___ \_____/ /_/ |_| /_/ |_| |_____| _____ _ _ _____ _____ / _ \ | | / / | ___| | _ \ | | | | | | / / | |__ | |_| | | | | | | | / / | __| | _ / | |_| | | |/ / | |___ | | \ \ \_____/ |___/ |_____| |_| \_\ """ raw_input("\n\nPress the enter key to exit.")

7. Using Quotes • You can use 2 single quotes (‘) • print ‘Hello’ • You can use 2 double quotes (“) • print “Hello” • Either one is fine • Quotes in quotes • print “Bill said to say ‘Hi!’” prints: Bill said to say ‘Hi!’

8. Newline • Just like in C/C++ the ‘\n’ goes to a new line • This allows you to space you output into a more readable form

9. Escape Sequences • The newline (\n) is called an escape sequence • The backslash character (\) indicates something special • It changes the meaning of the following character! • For example: • ‘n’ is just the letter (lowercase) n • ‘\n’ is a newline!

10. Other Escape Sequences • \\ Backslash (the first backslash indicates that the second backslash in just the normal backslash character!) • \’ Is just the character ‘ • NOT the beginning or end of a string • \” Is just the character “ • NOT the beginning or end of a string • \n is a newline (we saw this already!)

11. More Escape Sequences • \a Rings a bell • \b Is a backspace • \t Is a tab

12. Strings • A ‘string’ is just a sequence of characters • print ‘This is a string’ • Combine two strings by using the concatenate (+) operator • print ‘This is ‘ + ‘two strings combined’ • Repeating string • print “Pie” * 5 • PiePiePiePiePie • print ‘*’ * 80 • **********************************…**

13. 3rd Program # Personal Greeter # Demonstrates getting user input # Michael Dawson 1/13/03 name = raw_input("Hi. What's your name? ") print name print "Hi, " + name raw_input("\n\nPress the enter key to exit.")

14. Numbers • There are basically two kinds of number in Python • Integer • Floating point (has a decimal point in it) • Examples: • print 24 / 6 (answer 4 – integer arithmetic) • print 19 / 4 (answer 4 – integer arithmetic) • print 19.0 / 4 (answer 4.75 – floating point arithmetic)

15. Arithmetic • Integer arithmetic ALWAYS uses whole numbers (integers) • Like: …-1, 0, 1, 2, 3, … • Floating point arithmetic ALWAYS uses decimal numbers (real numbers) • Like: 3.1415, 97.32, … • If you combine integers and floating point numbers in the same line integers will be (automatically) converted to floating point numbers

16. Variables • A ‘variable’ is a way to store & reference some data • name = ‘frank’ • age = 21 • pi = 3.14159265358 • Unlike C/C++ & Java you do not have to ‘declare’ variables in Python • Simply use (reference) them

17. Input • To get input into your program we use the ‘raw_input’ command • name = raw_input(“Enter your name: “) • This will print out the text “Enter your name: “ and then allow your to enter your name • The program will wait as you type until you type a newline (carriage return) (Enter key)

18. String Methods • A ‘method’ is just object oriented name for some code (maybe with some data) • Example: • text = “This is some EXAMPLE text” • print text This is some EXAMPLE text • print text.upper() THIS IS SOME EXAMPLE TEXT • print text.lower() this is some example text

19. Some String Methods • upper () – returns upper case • lower() – returns lower case • swapcase() – changes upper to lower & lower to upper • capitalize() – first letter is upper & rest lower • title() – first character of each word is upper & rest is lower • strip() – remove all beginning & ending whites spaces (blanks, tabs, newlines) • replace(old,new,max) – replace ‘old’ with ‘new’. Optonal ‘max’ is the maximum times to do it

20. ConvertingStrings to integers • The input method ‘raw_input’ will input a string! How do you get a number!? • Example: • age = raw_input(“Enter your age: “) Note: age is a string! • age = int(age) Note: converts the string ‘age’ into an integer ‘age’

21. Conversions • float(x) – converts ‘x’ into a floating point number • int(x) – converts ‘x’ into an integer • str(x) – converts ‘x’ into a string

22. Assignment shortcuts • *= • x *= 5 (x = x * 5) • /= • x /= 5 (x = x / 5) • %= • x %= 5 (x = x % 5) • += • x += 5 (x = x + 5) • -= • x -= 5 (x = x – 5)

23. 4th Program # Useless Trivia # # Gets personal information from the user and then # prints true, but useless information about him or her # # Michael Dawson - 1/14/03 name = raw_input("Hi. What's your name? ") age = raw_input("And how old are you? ") age = int(age) weight = raw_input("Okay, last question. How many pounds do you weigh? ") weight = int(weight) print "\nIf poet ee cummings were to email you, he'd address you as", name.lower() ee_mad = name.upper() print "But if ee were mad, he'd call you", ee_mad

24. 4TH Program (cont…) dog_years = age / 7 print "\nDid you know that you're just", dog_years, "in dog years?" seconds = age * 365 * 24 * 60 * 60 print "But you're also over", seconds, "seconds old." called = name * 5 print "\nIf a small child were trying to get your attention, " \ "your name would become:" print called moon_weight = weight / 6.0 print "\nDid you know that on the moon you would weigh only", moon_weight, "pounds?" sun_weight = weight * 27.1 print "But on the sun, you'd weigh", sun_weight, "(but, ah... not for long)." raw_input("\n\nPress the enter key to exit.")

25. 5th Program # Guess My Number # # The computer picks a random number between 1 and 100 # The player tries to guess it and the computer lets # the player know if the guess is too high, too low # or right on the money # # Michael Dawson - 1/8/03 import random print "\tWelcome to 'Guess My Number'!" print "\nI'm thinking of a number between 1 and 100." print "Try to guess it in as few attempts as possible.\n" # set the initial values the_number = random.randrange(100) + 1 guess = int(raw_input("Take a guess: ")) tries = 1

26. 5th Program (Cont…) # guessing loop while (guess != the_number): if (guess > the_number): print "Lower..." else: print "Higher..." guess = int(raw_input("Take a guess: ")) tries += 1 print "You guessed it! The number was", the_number print "And it only took you", tries, "tries!\n" raw_input("\n\nPress the enter key to exit.")

27. Class Program • Write a Python program in class • Have the computer guess MY number • Develop program specification • Develop pseudocode for program • Write, test AND demonstrate Python program

28. Homework • Due Week 3 in Class • Write a Python Program to: • Accept a text message from the user and then prints it out backwards • Include: • Simple Specification Document • Simple Pseudocode • Python code • Demonstrate program in class