3.1 and 3.2 Variables, Assignments, and Data Abstractions

Variables

  • A variable is an abstraction in a program that can hold a value
  • Has three parts, name, value and type
  • Meaningful variables helps readability and understanding the code

Types of data

  • Integer: A number
  • String: A word
  • Boolean: True or False

Lists

  • Print multiple values without creating many variables
  • easily add and change values in the list

Assignments

  • The assignment operator allows a program to change the value represented by a variable
  • Used to assign values to a variable
  • Value that is stored in the variable is the one most recently assigned to it

Data Abstraction

  • Method in programing to represent data in a useful form, taking aspects of data that arent being used
  • Variables and lists are important for data abstraction

Lists and Strings

  • Element = individual value in the list
  • Index = a way to referance elements in a list

Managing Complexity in a Program

  • Data abstractions help by giving the collection a name without refrencing specific details

Ap Exam Use

  • Index questions do not start at 0, but 1
colorList=["green", "red", "pink", "purple", "blue", "brown"]
for i in range(len(colorList)):
	print(colorList[i])

green
red
pink
purple
blue
brown

def sort(testScores):
    # variable assigned to the length of the test score list
    length=len(testScores)
    # loops through the length of the test score list amount of times
    for i in range(length):
        for j in range((i+1),length):
            # checks in order of the list if the next value is greater than it or not, and swaps places if its less than it
            if testScores[i]>testScores[j]:
                l1=testScores[i]
                testScores[i]= testScores[j]
                testScores[j]=l1
    # once the whole list checks out, it outputs the score as a list
    print(testScores)
# list of scores                
testScoresList=[78,94,72,86,65,91,92,88,78,55]
# function being called
sort(testScoresList)

[55, 65, 72, 78, 78, 86, 88, 91, 92, 94]

3.3 and 3.4 Mathematical Expressions and Strings

Algorithm Steps

  • Sequencing
  • Selection

  • Iteration

  • Can be represented in two ways: Flow Charts, Pseudocode

Arithmetic Operation

  • for addition+, * multiplication, / division and - subtraction
  • Operations in parentheses should be done first
  • Division and multiplication should be done before addition and subtraction
  • Modules work similar to multiplication

Variables

  • Numerical value stored in a variable

Sequencing is Important

  • Assigning a variable will overide the last value which was assigned to the same variable.

Strings

  • A string is a collection of characters. It could be numbers and symbols, but it is still a string
  • len() finds the length of lists and strings
  • lower() to convert to lowercase
  • concat() returns a string made up on the concatenated strings

Hacks/Hw

Num1 = 50

Num2 = Num1 % 9 + 15

Num3 = Num2 / Num1 + ( Num2 * 2 )

Num4 = Num3 + Num1 / 5 - 10

Result = Num4 - Num2

Result = 20.4 ^^

Num1 = 10

Num2 = Num1 % 3 * 4

Num1 = Num2

Num3 = Num1 * 3

Result = Num3 % 2

Result = 0 ^^

valueA = 4

valueB = 90

valueC = 17

valueB = valueC - valueA

valueA = valueA * 10

if valueB > 10:

print(valueC)

Result = 17 ^^

type = "curly"

color = "brown"

length = "short"

type = "straight"

hair = type + color + length

print(hair)

Result = "straightbrownshort" ^^ 

Noun = "Mr.Mortenson" 
Adjective = "handsome" 
Adjective2 = "Very" 
Verb = "is" 
abrev = Noun[:7]
yoda = (Adjective2+ " "+ Adjective+ " "+ abrev+ " "+Verb+ ".") 
print(yoda)

# Result is "Very handsome Mr.Mort is."

Very handsome Mr.Mort is.

cookie = "choclate" 
cookie2 = "rasin" 
len1 = len(cookie) / 2 
len2 = len(cookie2) * 45
vote1 = (cookie, "vote", len2)
vote2 = (cookie2, "vote", len1)
votes = (vote1, " ", vote2)
print(votes)

# Result (('choclate', 'vote', 225), ' ', ('rasin', 'vote', 4.0))

(('choclate', 'vote', 225), ' ', ('rasin', 'vote', 4.0))

Unit 3 Sections 5-7