Understanding Basic Data Types

What are Data Types?

A data type is a classification that tells the program how the programmer intends to use the data. For instance, you can perform mathematical calculations on numbers, but you can't do the same with text. Python, being a dynamically typed language, is smart enough to figure out the data type on its own when you assign a value to a variable. You don't have to explicitly tell it, "this variable will hold a number."

Let's begin with a high-level overview of some of Python's built-in data types.

The Four Core Data Types

The video below from the GeoDelta Labs channel provides a great conceptual introduction to our four core data types. As you watch, pay attention to the definition of each type and the real-world examples given.

Let's quickly review and formalize these concepts.

1. Integers (int): These are whole numbers, without any decimal part. They can be positive, negative, or zero.

   
   
   
   # Examples of integers
   player_count = 4
   current_year = 2023
   account_balance = -50
   

2. Floating-Point Numbers (float): These are numbers that have a decimal point. They are used for values that require precision, like measurements or prices.

   
   
   
   # Examples of floats
   pi = 3.14159
   item_price = 19.99
   temperature = -2.5
   

   Even a number like 10.0 is a float because of the decimal point, distinguishing it from the integer 10.

3. Strings (str): A string is a sequence of characters used to store text. In Python, you create a string by enclosing the text in either single quotes ('...') or double quotes ("...").

   
   
   
   # Examples of strings
   user_name = "Alice"
   greeting_message = 'Hello, world!'
   error_code = "Error 404" 
   

   You can use either single or double quotes, but you must be consistent. user_name = "Alice' would cause a syntax error.

4. Booleans (bool): A boolean can only have one of two values: True or False. They are used to represent logical states, like whether a condition is met or an option is enabled.

   
   
   
   # Examples of booleans
   is_logged_in = True
   has_permission = False
   

   Crucially, these values are case-sensitive. true and false are not valid boolean values in Python and will cause an error. They must be capitalized as True and False.

How to Check a Variable's Type

Since Python determines the data type automatically, it's useful to have a way to check what type a variable holds. This is especially helpful when you're debugging code or trying to understand how a program works. Python provides a built-in function called type() for exactly this purpose.

The W3Schools page on Python Data Types provides a concise explanation.

To see this in practice, let's look at an image showing type() being used in a Python interactive shell.

Now, let's see a demonstration of type() being used for all four of our basic data types. The second half of the GeoDelta Labs video you watched earlier does exactly this.

Practice Exercise

It's time to put this into practice. Open your Python REPL (interactive shell) or create a new script file (datatypes.py).

1. Create a variable named book_title and assign it the string value of your favorite book.
2. Create a variable named page_count and assign it the number of pages in that book as an integer.
3. Create a variable named book_price and assign it the price of the book as a float.
4. Create a variable named is_read and assign it a boolean value (True or False) indicating whether you have read it.

After creating these four variables, use the print() and type() functions together to display the type of each variable. For example:

print(type(book_title))
print(type(page_count))



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

Running your code should output the class for each type: <class 'str'>, <class 'int'>, <class 'float'>, and <class 'bool'>.

Conclusion

In this lesson, you've been introduced to the fundamental building blocks of data in Python. You now know how to create and identify the four most common data types, which will be the foundation for almost every program you write.

Here are the key takeaways:

• A data type defines what kind of data a variable holds and what operations are allowed on it.
• The four basic data types are:
  • int: For whole numbers (e.g., 10, -5).
  • float: For numbers with a decimal point (e.g., 3.14, 99.0).
  • str: For text, enclosed in quotes (e.g., "hello", 'Python').
  • bool: For logical values, which must be True or False.
• You can use the built-in type() function to find out the data type of any variable.

Now that you have a solid understanding of numeric data types (int and float), our next lesson will focus on what you can do with them. We will explore arithmetic operations, learning how to perform calculations like addition, subtraction, multiplication, and division in Python.