Variables and Data Types in Python

What are Variables?

In programming, a variable is a name you give to a storage location in the computer's memory. This allows you to store a piece of data, refer to it, and manipulate it throughout your program using a descriptive name.

The primary way to create a variable in Python is through assignment, using the equals sign (=). The syntax is simple:

variable_name = value

To get a clear and practical introduction to this concept, let's start with a short video.

As you saw in the video, we can store different types of information in variables. Let's formalize these core data types.

The Four Fundamental Data Types

Every value in Python has a data type. While there are many, we will start with the four most basic and common ones. Understanding these is non-negotiable for writing any program.

1. Integer (int): Represents whole numbers, both positive and negative, without any decimal points.

   • Examples: 42, -150, 0

2. Float (float): Represents numbers with a decimal point, or floating-point numbers. These are used for values that require precision.

   • Examples: 3.14159, -0.001, 2.0

3. String (str): Represents a sequence of characters, or text. In Python, strings are enclosed in either single quotes ('...') or double quotes ("...").

   • Examples: "Hello, world", 'Python', "123" (Note: this is text, not a number)

4. Boolean (bool): Represents one of two logical values: True or False. These are crucial for decision-making in code. Note that the first letter is always capitalized.

   • Examples: True, False

This image provides a helpful visual summary of these data types.

To reinforce these concepts with more examples, let's watch another video. Seeing the same ideas presented differently can often deepen understanding.

Python's Approach: Dynamic Typing and Object References

You may have noticed that you don't have to tell Python the type of data a variable will hold. This is because Python is a dynamically typed language. It automatically figures out the data type at the moment you assign a value.

A deeper, more theoretical point that fits your theory-first preference is how Python handles this internally. In Python, variables don't contain the values directly. Instead, they hold a reference—like a pointer or a memory address—to an object that contains the actual data.

When you write age = 21, Python does the following:

1. Creates an integer object with the value 21.
2. Creates a variable named age.
3. Makes age refer to, or point at, that integer object in memory.

This is why you can reassign a variable to a completely different type of data later on.

x = 10         # x refers to an integer object
print(type(x)) # Output: <class 'int'>

x = "hello"    # Now, x refers to a string object
print(type(x)) # Output: <class 'str'>

The function type() is a built-in Python tool that tells you the data type of the object a variable is currently referencing.

To explore this crucial theoretical concept further, please read the following sections from a comprehensive article on Real Python.

Your Turn: Creating Variables in Python

Now it's time to apply what you've learned. An essential part of becoming a proficient programmer is writing clean, readable code from the very beginning. A key aspect of this is choosing good variable names.

Watch this final video clip, which covers best practices for naming your variables.

Hands-On Exercise

Open a Python environment (like a Jupyter Notebook, an online Python interpreter, or an IDE like VS Code). Your task is to create a set of variables that could describe a project, then print their values and types.

1. Create a variable named project_name and assign it a string value, for example, "JARVIS_AI".
2. Create a variable named version_number and assign it a float value, like 1.0.
3. Create a variable named build_year and assign it an integer value, such as 2024.
4. Create a variable named is_active and assign it a boolean value, True.
5. For each variable, use the print() function to display its value.
6. After printing the value, use print(type(...)) to display the data type of each variable.

Example Code Structure:

# Your code for project_name
print(project_name)
print(type(project_name))




# Your code for version_number
print(version_number)
print(type(version_number))




# ... and so on for the other two variables

After you run your code, your output should look something like this:

JARVIS_AI
<class 'str'>
1.0
<class 'float'>
2024
<class 'int'>
True
<class 'bool'>

This exercise directly confirms that you can successfully assign values and identify the corresponding data types, achieving our lesson's goal.

Conclusion

In this lesson, you took the first critical step in your programming journey. You learned how to use variables to store and label information, and you became familiar with the four most fundamental data types in Python.

Key Takeaways:

• Variables are names that refer to data stored in memory. You create them using the assignment operator (=).
• Python is dynamically typed, meaning the type of a variable is determined by the value it holds at runtime.
• The four basic data types are:
  • int for whole numbers.
  • float for numbers with decimals.
  • str for text.
  • bool for True or False values.
• Writing clean code with descriptive variable names is a professional habit to build from day one.

You now have the tools to represent data. The next logical step is to learn how to operate on that data.

Preview of the Next Lesson:
In the next lesson, we will explore Python operators. You will learn how to perform arithmetic (+, -, *, /) and make comparisons (==, !=, >, <). This will unlock your ability to perform calculations and make logical decisions in your code—a foundational skill for the complex problem-solving required in AI.