What Are Variables?

• Variables are like containers that store data in your program. They hold values that you can use, change, and refer to throughout your code.

Creating and Assigning Variables:

• In Python, you don’t need to specify the type of data when creating a variable.

• Just assign a value to a variable name:

  

  variable_name = value
  

  • Examples:

    

    message = "Hello World"
    quantity = 20
    pi = 3.14
    

Reassigning Variables:

• You can change the value of a variable, even to a different type:

  

  x = "Hello World"
  x = "Good Morning"
  x = True
  

Using Variables in Expressions:

• You can use variables in calculations and expressions:

  

  a = 10
  b = 20
  c = a + b
  print('c is ', c)
  

  • Output: c is 30

Naming Rules for Variables:

1. Valid Characters: Use letters, numbers, and underscores (_). Must start with a letter or underscore.
2. No Spaces or Special Characters: Avoid spaces and symbols like !, @, #, etc.
3. Case Sensitivity: Python treats my_variable and My_variable as different variables.
4. Avoid Reserved Words: Don’t use keywords like if, else, while, etc.
5. Descriptive and Readable: Use meaningful names like user_name or total_amount.
6. Snake Case: For multiple words, use snake_case: user_name.
7. Leading Underscore: _variable suggests it’s private.
8. Double Underscore: __variable is used for name mangling in classes.

Printing the Value in a Variable:

• Use the print() function:

  

  a = "Hello World"
  print(a)  
  

  • Output: Hello World

Converting the Value in a Variable:

• Convert types using functions like str(), int(), float():

  

  x = 236.52142
  x = int(x)
  print(x)  

  • Output: 236

Getting the Type of a Value in a Variable:

• Use the type() function to find out the type:

  

  x = 236.52142
  print(type(x)) 

  • Output: <class 'float'>

Summary:

• Variables are essential for storing and managing data in Python. Understanding how to create, assign, and use variables will help you write effective Python code. Try the examples and exercises to get hands-on practice!