Variables and Data Types

In programming, variables are used to store and manipulate data. They act as containers that hold values, allowing us to refer to that data by its assigned name. Python is a dynamically-typed language, meaning that you don’t need to explicitly declare the data type of a variable before using it. Instead, the data type is automatically inferred based on the value assigned to the variable.

Variable Naming Rules

When naming variables in Python, there are certain rules you must follow:

• A variable name must start with a letter or an underscore (_).
• A variable name cannot start with a number.
• A variable name can only contain alphanumeric characters (a-z, A-Z, 0-9) and underscores (_).
• Variable names are case-sensitive. For example, “myVariable” and “myvariable” are considered different variables.

It’s important to choose descriptive variable names that convey the purpose or meaning of the data they store. This makes your code easier to understand and maintain.

Data Types

Python has several built-in data types that are used to represent different kinds of values. Here are some commonly used data types:

Numeric Data Types:

Python supports three numeric data types:

• Integers: Integers are whole numbers, such as 1, 2, -5, etc. They are represented using the int data type in Python.
• Floats: Floats are numbers with decimal points, such as 3.14, -2.5, etc. They are represented using the float data type in Python.
• Complex: Complex numbers are a combination of a real and an imaginary part, represented as a + bj, where a and b are floats and j represents the square root of -1. Complex numbers are represented using the complex data type in Python.

Text Type:

The string data type is used to represent text in Python. A string is a sequence of characters enclosed in either single quotes (”) or double quotes (“”). For example, 'Hello' and "World" are both strings. Strings are immutable, which means that once created, they cannot be changed.

Boolean:

A boolean data type represents either True or False values. Booleans are often used in conditional statements and comparisons. For example, the statement 2 > 1 evaluates to True.

Sequence Types:

Python provides several sequence types to handle collections of values:

• List: A list is an ordered collection of items, represented using square brackets ([]). Lists can contain values of different types and can be modified after creation.
• Tuple: A tuple is an ordered collection of items, represented using parentheses (()). Tuples are similar to lists, but they are immutable, meaning their values cannot be changed once defined.
• Range: The range data type represents an immutable sequence of numbers, commonly used in for loops.

Mapping Type:

A dictionary is an unordered collection of key-value pairs. Each key in a dictionary must be unique, and it is used to access the corresponding value. Dictionaries are represented using curly braces ({}).

None Type:

The None type represents the absence of a value. It is often used to indicate a variable that has not been assigned a value yet or as a return value for functions that do not return anything.

Assigning Values to Variables

In Python, you can assign values to variables using the assignment operator (=). Here are some examples:

x = 5
name = "John"
pi = 3.14
is_student = True

Variables can also be assigned values based on the evaluation of expressions:

y = x + 2
area = pi * radius ** 2

It’s essential to understand that when you assign a value to a variable, you are not copying the data itself, but rather creating a reference to the data. Therefore, if you modify the value of a variable, all references to that variable will reflect the modified value.

With a solid understanding of variables and data types in Python, you are now equipped to start manipulating and working with data in your Python programs. Take the time to practice using different data types and experiment with assigning and modifying values to improve your understanding of these concepts.