Variables and Arrays

Jamie Z 2024-01-29

Learning Goals

By the end of this lesson I will be able to:

Understand what variables and arrays are
Understand how to use variables and arrays in python

Python Syntax

Indentation:

Indentation refers to the spaces at the beginning of a code line.
Where in other programming languages the indentation in code is for readability only, the indentation in Python is very important.
Python uses indentation to indicate a block of code.

if 5>2:
	print("5 is larger than 2")

Comments:

Python has commenting capability for the purpose of in-code documentation.
Comments start with a #, and Python will render the rest of the line as a comment:

#this is a comment
print("hellowowowow")

Data types

In python there are several built in data types that you can use to store different types of data

Integer: A whole number such as 1, 110 or 100
Float: A decimal number such as 3.14 or 0.01
String: A sequence of characters, such as “hello world”
Boolean: A value that can be either True or False

We will be able to store these different types of data in an array or list

Variables

A variable that can change, or be change, during the course of a program’s execution

x = 5
print(x)

Playing With Variables

Example

```python x = 5 y=10 #add variables z = x+y print(z) #subtract variables z = y-x print(z) #multiply variables z=x*y print(z) #divide variables z = y/x print(int(z)) ```

# What is an Array?

Variables are used to store information. But one variable can only store one piece of information at a time. However, you can use an Array to store lots of information.
Array start at index 0
To create an empty array, choose a name for your array and assign it a pair of empty square brackets like this:

Backpack = []

Arrays can also start with data being held, like the example below:

Backpack = ['water bottle', "umbrella", 'apple']

The things that an array stores are called elements. The Backpack array has three elements.

There are four main functions you will do with arrays this Term:

Create arrays
Add an element to the array
Remove an element from the array
Sort the Array

Example

```python # Create an array fruits = ['apple', 'banana', 'cherry']

Add an element to the array

fruits.append('date') print(fruits)

Remove an element from the array

fruits.pop(1) print(fruits)

Sort the array

fruits.sort() print(fruits)


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# Activity


Research and create your own python program that:

- Asks for your name
- Accepts a user input
- Stores the name
- Outputs it back to the user in a string that says “Hello, {name}. Welcome to your first Python Program.”

```python
name = input("What is your name?")
print(f"Hello, {name}. Welcome to your first Python Program")