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What are Variables?

In Python, a variable is a container used to store data. You can think of a variable as a box that holds a value. Each variable has a name, and you can use that name to access the value stored inside.

Creating a Variable

To create a variable, you simply choose a name for it and assign it a value. In Python, we use the = sign to assign a value to a variable.

Example:

age = 25

In this example:

  • age is the name of the variable.
  • 25 is the value stored in the variable.

Printing the Value of a Variable

To see the value stored in a variable, you can use the print() function.

Example:

age = 25
print(age)

Sample Output:

25

Types of Values

Python variables can store different types of values. Here are the most common types:

  1. Numbers:
    • Integers: Whole numbers.
    • Floats: Decimal numbers.

Example of both:

age = 25        # Integer
height = 5.7    # Float
  1. Text (Strings): This is used to store words or sentences. A string is enclosed in quotes.

Example:

name = "John"
  1. Booleans: These represent two values, True or False.

Example:

is_student = True
  1. Lists: A list is an ordered collection of items, which can be numbers, strings, or other variables.

Example:

fruits = ["apple", "banana", "cherry"]
  1. Dictionaries: A dictionary is a collection of key-value pairs.

Example:

person = {"name": "John", "age": 25}

Changing the Value of a Variable

Once you’ve created a variable, you can change its value by simply assigning a new value to it.

Example:

age = 25
print(age)

age = 30
print(age)

Sample Output:

25
30

Variable Naming Rules

There are some rules for naming variables in Python:

  1. Variable names can only contain letters, numbers, and underscores (_).
  2. A variable name must start with a letter or an underscore, not a number.
  3. Variable names are case-sensitive, meaning age and Age are two different variables.
  4. You cannot use Python reserved words like True, False, if, else, class, etc.

Dynamic Typing

Python is dynamically typed, which means you don’t need to specify the type of a variable when you create it. Python automatically determines the type based on the value assigned to the variable.

Example:

my_var = 10       # Python sees this as an integer
my_var = "Hello"  # Now, Python sees this as a string

Multiple Variables in One Line

You can assign values to multiple variables in one line by separating them with commas.

Example:

name, age, height = "John", 25, 5.7
print(name)
print(age)
print(height)

Sample Output:

John
25
5.7

Constants

In Python, variables are usually not constant, meaning you can change their value. However, you can create a variable that should not be changed by convention. In Python, this is done by writing the variable name in all capital letters.

Example:

PI = 3.14159

Example of Using Variables Together

You can use variables together in expressions, like math calculations or combining text.

Example:

first_name = "John"
last_name = "Doe"
age = 25

full_name = first_name + " " + last_name
print(full_name)

years_to_100 = 100 - age
print("Years to 100:", years_to_100)

Sample Output:

John Doe
Years to 100: 75
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