Python Crash Course by Monica Sweat

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

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

Starting Simply can use IDLE / python as a calculator >>> >>> 4 ** 2 16 >>> 6 / 2 3 >>> 1 / 2 0  gotcha that begs an introduction to types

Common Types sampling of types – int signed integer, 32 bits, ±2,147,483,647 – longarbitrarily long ends with L – float64 bit double precision, like 1.23 or 7.8e- 28 – strdelimit in ' or " – bool Booleans True and False type(x) yields the type of the data stored currently in variable x

str Type str is the type for strings in python they can be single quote or double quote delimited word = "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."""

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 Sweat July 8, 2008"""

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

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

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"

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

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

Printing Results Increasingly better ways to print pay hours = 35 rate = 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

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

Getting Input from the User numeric input age = input("Age? ") string input name = raw_input("Name? ")

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)

Conditionals if if/else if/elif/elif/elif/…/else all branches use colon : all bodies are indented Python uses indentation to denote blocks.

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

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

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

Using Modules import math def circleArea(radius): area = math.pi * radius ** 2 return area math, random, re, os, …

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

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]

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

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

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

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

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]

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) (3 rd parameter is step value) [0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50]

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

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

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