Python

1. Python Crash Course by Monica Sweat

2. Python Perspective • is strongly typed, interpreted language • is used to define scripts(Don't even need to define a function proper.) • is used to define functions • can be used in object-oriented style • is an up and coming real language in industry

3. Integrated Development Environment: IDLE • IDLE is provided with standard python installation • available for virtually any platform • provides an editing window • provides an interactive interpreter window

4. Starting Simply can use IDLE / python as a calculator>>> 3 + 412>>> 4 ** 216>>> 6 / 23>>> 1 / 20  gotcha that begs anintroduction to types

5. Common Types • sampling of types • int signed integer, 32 bits, ±2,147,483,647 • long arbitrarily long ends with L • float 64 bit double precision, like 1.23 or 7.8e-28 • str delimit in ' or " • bool Booleans True and False • type(x)yields the type of the data stored currently in variable x

6. str Type • str is the type for strings in python • they can be single quote or double quote delimitedword = "can't" • multiline strings can be triple quoted (that's 3 single quotes or 3 double quotes in a row)poem = """Roses are red,violets are blue."""

7. Comments (relates to strings) • comments in python are single line and use the # symbol# This program written by George Burdell • multiline comments can be faked by using the triple quoted string trick"""This program written by Monica SweatJuly 8, 2008"""

8. Math Operations • () parens for grouping • + - unary plus, minus • ** exponentiation • * / % mult-style ops • + - add, subtract

9. Simple Demo of Variables >>> age = 18 >>> print age 18 >>> age = age + 1 >>> print age 19

10. Python Variables • Python is case-sensitive • variable names • function names • everything • Camel case is a common style in python, java, etc. firstName = 'George' lastName = 'Burdell' print firstName, lastName word = "don't"

11. Python Variables • [a-zA-Z][a-zA-Z0-9 _]* • start with letter followed by letters and digits • any length • case matters • do not have to be declared! • python is strongly typed, but the "type" is bound to the data and not the variable

12. Script Example Complete script using variables Assignment statement uses = hours = 35 rate = 25.50 pay = hours * rate print pay

13. Printing Results Increasingly better ways to print pay hours = 35 rate = 25.50 pay = hours * rate print pay or print "Your pay is", pay or print "Your pay is $" + str(pay) or print "Your pay is $%.2f" % pay

14. Easy User Input Use input for console input of a numeric value hours = input("How many hours? ") rate = input("Pay rate? ") pay = hours * rate print "Your pay is $%.2f" % pay

15. Getting Input from the User • numeric inputage = input("Age? ") • string inputname = raw_input("Name? ")

16. Type Conversion • x = int(3.9) • y = float(5) • print "Answer: " + str(2 * 3)(Useful if concatenating with a string) • age = int(raw_input("Age? "))(Useful if using raw_input to get all input from the user.) • average = float(sum)/float(total)(Forces float division)

17. Conditionals • if • if/else • if/elif/elif/elif/…/else • all branches use colon : • all bodies are indentedPython uses indentation to denote blocks.

18. Building Conditions • relational operators as expected<, >, <=, >=, ==, !=, <>(assignment uses single equals sign) • logical operators are lowercasenot, and, or(! can be used for not) • parentheses not necessary unless overriding precedence

19. Conditionals age = input("Age? ") if age <= 12: ticketPrice = 5 elif age >= 65: ticketPrice = 7.5 else: ticketPrice = 9 print ticketPrice

20. Defining a Function def rectangleArea(length, width): area = length * width return area

21. Using Modules import math def circleArea(radius): area = math.pi * radius ** 2 return area http://docs.python.org/modindex.html math, random, re, os, …

22. Importing Modules import math print math.pi x = math.sqrt(9) vs. from math import pi, sqrt print pi x = sqrt(9)

23. Python Sequences (arrays) • python's answer to the array • is dynamic • behaves like a linked listed with indexing names = ["Fred", "Wilma"] names[0] = "Barney" print names[0]

24. Python Sequences (arrays) common operations (there are many) names = names + ["Dino"] or names.append("Bambam")

25. for Loop for-each style iterates through a sequence syntax: for item in sequence: block-of-code for flavor in ["chocolate", "vanilla"]: print "I like", flavor

26. for Loop def average(array): sum = 0 count = 0 for num in array: sum = sum + num count = count + 1 return float(sum)/count

27. Counting-style for Loop for loop with counting style using range: for num in range(1, 5): print num Output: 1 2 3 4

28. Processing Array without/with range for-each style to iterate through a sequence: for flavor in ["chocolate", "vanilla"]: print "I like", flavor vs. index-driven style processing a sequence: flavors = ["chocolate", "vanilla", "mint"] for index in range(len(flavors)): print "I like", flavors[index]

29. range Function Details • most commonly used to generate indices for iterating a sequence • may have 1, 2, or 3 parameters • stopping value is exclusive >>> range(5)(starts at 0 if one parameter) [0, 1, 2, 3, 4] >>> range(1995, 2000)(stopping value exclusive) [1995, 1996, 1997, 1998, 1999] >>> range(0, 55, 5) (3rd parameter is step value) [0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50]

30. range Function to Generate Data def summation(n): total = 0 for num in range(n + 1): total = total + num return total

31. while Loop number = 1 while number <= 5: print number number += 1

32. myro – Major Bonuses • myro defined as a proper module • programmer imports it as they would any module • natural way to incorporate added functionality • works with standard python • all of standard python is available to the user • other modules: math, random, os, etc are still available • materials for python still apply