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Variables

This section will cover Python Variables.

Table of Contents​
  • Overview
  • Names
    • Camel Case
    • Pascal Case
    • Snake Case
  • Assigning Values to Multiple Variables
    • One Value to Multiple Variables
    • Unpack a Collection
  • Output Variables
  • Global Variables

Overview​

A variable in Python can have a short, descriptive, or long name. The name depends on the developer. However, there are a few rules to keep in mind when creating variables in Python.

The rules:

  • The name must start with a letter or the underscore (_) character.
  • A variable name cannot start with a number.
  • A variable name can only contain alpha-numeric characters and underscores.
  • Variable names are case-sensitive (name, Name, and NAME are three different variables).
  • A variable name cannot be any of the Python keywords.

Names​

The below are some examples of legal variable names.

myvar = "var1"
my_var = 'var2'
_my_var = "var 3"
myVar = "legal 1"
MyVar = "legal 2"
MYVAR = "legal 3"
myvar7 = "var4"

Examples of illegal names are:

my var = "var with space"
my-var = "var with dash"
1myvar = "var that starts with a number"

For easier readability, the coder can use different techniques to make it more readable.

Camel Case​

Each word except the first, starts with a capital letter.

thisIsMyVar = "Test"

Pascal Case​

Each word starts with a capital letter.

ThisIsAnotherVar = "Pascal"

Snake Case​

Each word is separated by an underscore.

snake_case_var = "snake var"

Assigning Values to Multiple Variables​

We can assign multiple variables in a single line.

a, b, c = "Var 1", "Var 2", "Var 3"

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

One Value to Multiple Variables​

We can assign the same value to multiple variables in a single line.

x = y = z = "multiple"

print(x)
print(y)
print(z)

Unpack a Collection​

If we have a collection of values such as lists or tuples, we can extract the values into variables. This is called unpacking.

my_shopping_list = ["chips", "water", "rice"]
a, b, c = my_shopping_list

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

Output Variables​

We can use functions such as print() to output the value assigned to the variable.

x = "Output test"
print(x)

To output multiple values, we can separate them with a comma or use use the plus (+) operator.

x = "My "
y = "variable "
z = "here"

print(x, y, z)
print(x + y + z) #Without the space in the x and y variable value, it will be a single word.

When dealing with numbers, the plus (+) operator acts as a math operator. When attempting to use a variable with a number and string, we will be given an error.

x = 10
y = 20
z = "math"

print(x + y)
print(x + z)

To overcome this, the best way will be using commas (,) to output multiple variables as it works with different data types.

Global Variables​

Global variables are variables created outside functions. Global variables can be used by everyone, both inside and outside functions.

var = "var1"

def myfunc():
	print("This is" + x)

myfunc()

If the variable is created inside a function with the same name, it will be local and can only be used inside the function unless the global keyword has been used.

#No global keyword
x = "global var"

def myfunc():
	x = "local var"
	print("This is my " + x)

my func()
print ("This is my " + x)

#Using the global keyboard
def myfunc():
	global y
	y = "local var 2"
	print("This is my " + y)

my func()
print("This is my " + y)