3.1.1 - What are variables
Sharon Kodali
Variables: an abstraction inside a program that can hold a value
A variable can be thought of as a container or a box that holds information that your program can use or modify
Variables help you manage and organize your work with data, making your code more organized, readable, and adaptable.
different data types to store variables in
- integer used to store numbers that can later be used in mathematical operations ex: age or temperature
- Text(string) Used to store texts lists and words that can later be referenced ex: Name, phone number, or address
- Boolean used to store simply of true or false ex: is it raining
Correct way to name variables
incorrect: my highs-coreinthegame or n
- too long and can make the code messy
- dashes are not allowed when naming variables
- spaces are not allowed when naming variables
- descriptive enough to easily recall what the variable repersents
correct: highscore or numstudents or israining
- short
- descriptive
- easy to distingush type of variable
3.1.1 Hacks
instructions: Determine what would be the the best variable name and data type for the specific prompt
- storing if someones pet is a dog
- storing someones birthday
- storing the amount of money someone is spending
- storing if it is sunny
Homework: write a greeting using variables in python
Naming Conventions
- Must start with a letter or an underscore
- Cannot start with a number
- Can only have alphanumeric characters or underscores
- Are case sensitive
- Cannot be python keywords such as 'else'
myName = "Tara"
print(myName)
Tara
1Tara = "16"
Cell In[2], line 1
1Tara = "16"
^
SyntaxError: invalid decimal literal
myAge = 16
myage = 46
print(myAge)
print(myage)
else = 22
Primitive v. Collection Data Types
Primitive Data Types
- int
- string
- float
- boolean
Collection Data Types
- list
- dictionary
myInt = 20
myString = "My name is Tara"
myFloat = 77.29
myBool = False
agesOfMyFriendsList = [16, 20, 15, 12]
print(agesOfMyFriendsList)
agesOfMyFriendsDictionary = { "Tara" : 16, "Tanisha" : 15, "Dylan" : 12, "Tara " : 17}
print(agesOfMyFriendsDictionary["Tara"])
print(agesOfMyFriendsDictionary["Tara "])
Concatenation
‘Joining’ of strings and other types
myFirstName = "Tara"
myLastName = "Sehdave"
print(myFirstName + " " + myLastName)
myFirstInt = 5
mySecondInt = 10
print(myFirstInt + mySecondInt)
Formatting allows us to display values using pre-decided rules
message = "My first name is {0} and my last name is {1}"
print(message.format("Tara", "Sehdave"))
print(message.format("Tanisha", "Patil"))
x = .77
message = "Show this as a percentage {0:.0%}"
print(message.format(x))
print(message.format(.25))
message = "The binary value of {0} is {0:b} and the binary value of {1} is {1:b}"
print(message.format(7, 6836))
Conversions
import json
myDictionary = {"A": 1, "B": 2}
print(myDictionary)
myStringDictionary = json.dumps(myDictionary)
print(myStringDictionary)
myDictionaryRecreated = json.loads(myStringDictionary)
print(myDictionaryRecreated)
# Python Data Types in CB Pseudo Code
## Primitive Types
a <-- expression
- myInt <-- 18
- myString <-- "My name is Tara"
- myFloat <-- 6.8
- myBool <-- False
# Collection Types
- myList <-- [1, 2, 3]
- No dictionary
Data Type Practice
Question 1: Integer Operation
- Declare two integer variables,
num1Intandnum2Int, and assign them values of your choice. - Calculate the sum of
num1Intandnum2Int - Print the sum
Question 2: Float Operation
- Declare two float variables,
float1andfloat2, and assign them values of your choice. - Calculate the quotient of ‘float1’ and ‘float2’
- Print the quotient
Question 3: Format Manipulation
- Write a message that equals a sentence with two placeholder variables
- Write two strings with two placeholder variables to insert into the message
- Print that message
Answers
# Integer Operations
num1Int = 16
num2Int = 12
print(num1Int + num2Int)
# Float Operation
float1 = 1.00
float2 = .75
print(float1 / float2 )
# Format Manipulation
message = "{0} is {1} years old"
print(message.format("Tara", "16"))
print (message.format("Sharon", "8"))
print (message.format("Dylan", "80"))
☆ Topic 3.2 ☆
☆ Using lists as an abstraction to manage a program's complexity
☆ learn about the lists section of the exam reference sheet
Things to remember
- use lists to store multiple elements
- data abstraction provides a seperation between abstract parts of a datatype and the actual details of it
- it can be created using lists
- the exam reference sheets has list notations
- the reference sheet has a list structure with index values 1-#of elements in the list. if list index is less that 1 or greater than the list
- variables must be bundled together
- strings, characters, words, numbers
- give one name to a set of cells
num =[1, 2, 3, 4]
abc = ["a", "b", "c"]
colors = ["red", "green", "blue"]
emptylist = []
#replacing
alist = [10, 20, 30, 40, 50]
blist = [20, 40, 60, 80, 100]
alist = blist
print(alist)
#what will be the output of this code?
%%javascript
# Define an array with elements
const colors = ["Red", "Green", "Blue", "Yellow"];
# Access elements using indexes
const firstColor = colors[0]; // Index 0: "Red"
const secondColor = colors[1]; // Index 1: "Green"
# Modify an element at a specific index
colors[2] = "Purple"; // Index 2 is changed from "Blue" to "Purple"
# Add a new element to the array
colors.push("Orange"); // Adds "Orange" to the end of the array
# Print elements and their indexes
console.log("First Color:", firstColor);
console.log("Second Color:", secondColor);
console.log("Updated Colors Array:", colors);
# Define a string
const greeting = "Hello, World!";
# Print the string
console.log(greeting);
3.2.3 Data Abstraction
-Manages complexity of data collection -Program easier to develop and maintain -Lists -If a list index is less than 1 or greater than the length of the list, an error message will be produced
How lists help with complexity
-Less variables (like one variable that holds multiple numbers instead of one variable for each number) -Changes number of variables -Consistency -Helps readability
Example
variable1 = 2 variable2 = 5 variable3 = 4
Would be simplified like this!
scores = [2, 5, 4]
Activity - Turn this into a list!
variable1 = 7 variable2 = 9 variable3 = 2 variable4 = 8
%%html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Grocery List</title>
</head>
<body>
<!-- Grocery List Title -->
<h1 id="storeTitle">Grocery List</h1>
<!-- Grocery List -->
<ul id="groceryList">
<li>Apples</li>
<li>Bananas</li>
<li>Carrots</li>
<li>Oranges</li>
<li>Milk</li>
</ul>
<!-- Swap Items Form -->
<div>
<input type="text" id="item1Input" placeholder="Item 1">
<input type="text" id="item2Input" placeholder="Item 2">
<button id="swapItemsButton">Switch Items</button>
</div>
<!-- JavaScript Code -->
<script>
// Function to swap two list items
function swapItems() {
var item1Input = document.getElementById("item1Input").value;
var item2Input = document.getElementById("item2Input").value;
var groceryList = document.getElementById("groceryList");
var items = groceryList.getElementsByTagName("li");
var item1, item2;
for (var i = 0; i < items.length; i++) {
if (items[i].innerText === item1Input) {
item1 = items[i];
}
if (items[i].innerText === item2Input) {
item2 = items[i];
}
}
if (item1 && item2) {
var item1Index = Array.from(items).indexOf(item1);
var item2Index = Array.from(items).indexOf(item2);
// Swap the items
groceryList.insertBefore(item1, items[item2Index]);
groceryList.insertBefore(item2, items[item1Index]);
// Update the title
var storeTitle = document.getElementById("storeTitle");
storeTitle.innerText = "Grocery List (Switched)";
}
}
// Attach the swapItems function to the button click event
var swapItemsButton = document.getElementById("swapItemsButton");
swapItemsButton.onclick = swapItems;
</script>
</body>
</html>
<!DOCTYPE html>
Grocery List
- Apples
- Bananas
- Carrots
- Oranges
- Milk