Layla

Python Basics: Variables, Literals and Constants 😎

Cover Image for Python Basics: Variables, Literals and Constants 😎

Howdy, thanks for checking out this Python beginners article! 😃 If you haven't read Part 1 in this series, you can check it out here!

But, if you've already read Part 1...
LET'S GET ROLLIN'! 😛

Check out the Table of Contents below to see what we'll be going over in Part 2 ⬇️

Table of Contents

Variables

A variable is a named location used to store data in memory. Think of variables like a container that holds data and can be changed later in the program. See below ⬇️ 

item = 200

Above, I created a variable named item and assigned the numerical value of 200 to it!

I usually think of variables as a grocery basket with items inside and any of the items can be replaced at any time.

We can easily rewrite variable assignments like so ⬇️ 

item = 100
item = 1.1

Initially, the variable item had a value of 100, but was rewritten to represent the value 1.1

Assigning Values to Variables

Declaring and assigning values to variables is super easy in Python! Here's an example below ⬇️ 

website = "seymourbutts.com"
print(website)

And the output:

seymourbutts.com

I assigned a value seymourbutts.com to the variable website. Then, I printed out the value assigned website i.e. seymourbutts.com!

Now, if you decide you want to change the value of your variable, that is also super easy! Check it out ⬇️ 

# assign initial value to website 
website = "seymourbutts.com"
print(website)

# assigning a new value to website
website = "udemy.com"

print(website)

And the output:

udemy.com

But, what if you need to assign multiple values to multiple variables? Look below ⬇️ 

a, b, c = 10, 12.2, "Howdy"

print (a)
print (b)
print (c)

Output:

10
12.2
Howdy

You an also assign the same value to multiple variables! 

d = e = f = "same"

print (d)
print (e)
print (f)

Output:

same
same
same

Constants

Constants are a variable, but they cannot be changed. Think about constants like your grocery basket of items, it holds your groceries, which can't be replaced! These are perfect for values that need to be referenced in your code, but you don't plan on changing. 😎

For example, in a grocery list calculator, a constant would be SALES TAX = 6.25 or in a math calculator program, PI = 3.14. Constants are usually capitalized to prevent them from getting confused with normal variables.

Here's an example of declaring a constant ⬇️ 

PI = 3.14

Now, let's talk about rules for naming variables & constants!

  • Give constants and variables a combination of letters in lowercase (a to z) or uppercase (A to Z) or digits (0 to 9) or an underscore (_)!

Like so:

snake_case
MACRO_CASE
camelCase
CapWords
  • Create a name that makes sense for the program you're creating! Like: groceries makes more sense than g!
  • Use underscore (_) if you want to create a variable with two or more words! Like: my_name or grocery_list!
  • Use capital letters to declare constants. Like: GRAVITY = 9.7

Literals

Literals are raw data given in a variable or constant. There's numerous types of literals in Python, but don't worry-- we'll break 'em down 😎

Numeric Literals

Numeric literals are immutable (unchangeable). Numeric literals can belong to 3 different numerical types: Integer (whole numbers) , Float (decimal numbers), and Complex (complex numbers are in the form x + yi).

So, how do you use numeric literals in Python? Check it out below ⬇️ 

a = 0b1010 #Binary Literals
b = 1000 #Decimal Literal 
c = 0o310 #Octal Literal
d = 0x12c #Hexadecimal Literal

#Float Literal
float_1 = 10.5 
float_2 = 1.5e2

print(a, b, c, d)
print(float_1, float_2)

Output:

10 100 200 300
10.5 150.0

Breakdown:

  • I assigned integer literals into different variables above. In the first block of code, a is a binary literal, b is a decimal literal, c is an octal literal and d is a hexadecimal literal.
  • In the second block of code commented #Float Literal, 10.1 and 1.5e2 are floating-point literals. 1.5e2 is expressed with exponential (the e stands for exponential) and is equivalent to 1.5 * 102

String Literals

A string literal is a line of characters surrounded by quotes. We can use both single, double, or triple quotes for a string. And, a character literal is a single character surrounded by single or double quotes!

So.. how do you use string literals in Python? Check it out below ⬇️ 

strings = "I love Python"
char = "C"
multiline_str = """This is a multiline string with more than one line of code!"""
unicode = u"\u00dcnic\u00f6de"
raw_str = r"look! it's a \n string"

print(strings)
print(char)
print(multiline_str)
print(unicode)
print(raw_str)

Output:

I love Python
C
This is a multiline string with more than one line of code!
Ünicöde
look! it's a \n string

Alright, here's the breakdown:

  • I love Python is a string literal and C is a character literal.
  • The value in triple-quotes """ assigned to the multiline_str is a multi-line string literal.
  • The string u"\u00dcnic\u00f6de" is a Unicode literal which supports characters other than English. In this case, \u00dc represents Ü and \u00f6 represents ö.

Hold on, folks...we're almost done with Literals!

Boolean Literals

These are simple (thank the heavens!): A Boolean literal can have any of the two values, True or False. Most importantly! True = the value of 1 and False = the value of 0.

How do we use boolean literals in Python? Check it out ⬇️ 

x = (1 == True)
y = (9 == False)
a = True + 5
b = False + 10

print("x is", x)
print("y is", y)
print("a:", a)
print("b:", b)

Output:

x is True
y is False
a: 6
b: 10

Breakdown:

  • In the code above, I used a boolean literal True and False. (Don't forget: in Python, True equals the value 1 and False equals 0.) The value of x is True because 1 is equal to True. And, the value of y is False because 1 is not equal to False.

  • Similarly, I used True and False with numeric expressions as their value. The value of a is 5 because we add True which has a value of 1 with 4. And b is 10 because we add False, which has a value of 0, to 10.

Special Literals

This one is fun! 😉 Python contains one special literal --> None. We use it to specify that the field haven't been created yet! Check out an example ⬇️ 

drink = "Available"
appetizer = None

def menu(x):
    if x == drink:
        print(drink)
    else:
        print(appetizer)

menu(drink)
menu(appetizer)

Output:

Available
None

Breakdown:

  • I defined a menu function. Inside menu, when we set the argument as drink then, it displays Available. And, when menu()'s argument is appetizer, it displays None!

You're done!! 🎉😆

In Part 3, I'll be going over:

  • All the Python Operators (arithmetic, logical, assignment operators)
  • Input, Output and Import (how to take input from the user, save it to a variable, display output, and import other Python modules) 😊

We're soo close to writing our first block of Python code!!!! Whoooop!! 😎 See you next week ❤️