Variables

 Variables

In Python, variables are used to store and manage data. Variables are like containers or labels that you can assign values to, and you can change the value stored in a variable during the program's execution. Here are some important points to know about variables in Python:

1. Variable Naming Rules:

   - Variable names must start with a letter (a-z, A-Z) or an underscore (_).

   - The remaining characters in the variable name can include letters, numbers (0-9), and

        underscores  ( _ ).

   - Variable names are case-sensitive, so `myVar` and `myvar` are considered different variables.

   - Python has reserved keywords that cannot be used as variable names.

2. Assigning Values:

   - You can assign a value to a variable using the assignment operator (`=`).

   - Variable assignment does not require specifying a data type explicitly; Python infers the data type dynamically.

   ```python

   my_var = 42

   name = "John"

   pi_value = 3.14159

   is_valid = True

   ```

3. Data Types:

   - Variables can hold various data types, including integers, floats, strings, booleans, lists, dictionaries, and more.

   - You can change the data type of a variable by assigning a value of a different type to it.

   ```python

   x = 10        # Integer

   y = 3.14      # Float

   name = "Alice"  # String

   is_valid = True  # Boolean

   ```

4. Dynamic Typing:

   - Python is dynamically typed, meaning you don't need to declare the data type of a variable explicitly.

   - The data type of a variable is determined at runtime based on the value it holds.

5. Reassigning Variables:

   - You can change the value of a variable by simply assigning a new value to it.

   ```python

   x = 5

   x = "Hello"

   ```

6. Multiple Assignments:

   - Python allows multiple assignments in a single line.

   ```python

   a, b, c = 1, 2, 3

   ```

7. Global and Local Scope:

   - Variables can have different scopes. Variables defined outside of functions have global scope and can be accessed from anywhere in the program.

   - Variables defined inside functions have local scope and can only be accessed within that function.

   ```python

   global_var = 10  # Global variable

   def my_function():

       local_var = 5  # Local variable

   ```

8. Constants:

   - While Python does not have constants in the same sense as some other languages, it is a convention to use uppercase names for constants and avoid reassigning them.

   ```python

   PI = 3.14159

   ```

9. Deleting Variables:

   - You can delete a variable using the `del` statement.

   ```python

   x = 10

   del x

   ```

Understanding how to work with variables is fundamental to programming in Python, as they are used to store and manipulate data throughout your code.