Variables in Python have a data type that determine what kind of value it holds and what you can do with it. If you’re working with data, understanding data types is important.

Last week, we introduced the dataset we’ll be using throughout the series. We’ll return to it soon, but first, we need to understand some additional aspects of Python, especially how it handles different types of data.

Common Data Types in Python

Python has several built-in data types. Below are the most commonly used ones.

1. Strings (str) – Used for text values

name = "Alice"  # A string (text value representing a name)
print(name)  # Output the string value

2. Integers (int) – Used for whole numbers

age = 25  # An integer (a whole number representing age)
print(age)  # Output the integer value

3. Floats (float) – Used for decimal numbers

height = 5.7  # A floating-point number (a decimal representing height)
print(height)  # Output the float value

4. Booleans (bool) – Used for True/False values

is_student = True  # A boolean (True/False value indicating student status)
print(is_student)  # Output the boolean value

5. None Type (NoneType) – Represents a missing or undefined value

grade = None  #  This means "no value"
print(grade)  # Output None

A quick note on NonType

None is a special value in Python that means “nothing” or “no value here.” When you assign a variable to None, Python gives it the data type NoneType.

It’s more of a descriptive way to refer to a variable that doesn’t hold a value of a built-in type like int, float, str, list, dict, bool, etc.

It’s useful when:

• You want to say “this doesn’t have a value yet.”
• A function doesn’t return anything.

You might hear someone say a variable is “non-type,” but what they really mean is that the variable’s value is None.

How to Check a Variable’s Data Type

Use the type() function to find out what kind of value you’re working with.

Its pretty much all the same thing, but i’m showing it here for emphasis. because you always want to check what type of value you are working with. You will realize the importance of this when you are working with a dataset where values might (intentionally or unintentionally) have unexpected types.

print(type(name))  # Check the type of a string variable
print(type(age))  # Check the type of an integer variable
print(type(height))  # Check the type of a float variable
print(type(is_student))  # Check the type of a boolean variable
print(type(grade))  # Check the type of a NoneType variable

Converting Between Data Types

Sometimes, you need to change or convert a variable’s data type. This is called type conversion.

1. Converting a String to an Integer

num_str = "100"  # A string containing numeric characters
num_int = int(num_str)  # Convert to an integer for numerical operations
print(num_int, type(num_int))  # Output converted integer and its type

2. Converting an Integer to a Float

num = 42  # A whole number (integer)
num_float = float(num)  # Convert to a floating-point number
print(num_float, type(num_float))  # Output converted float and its type

3. Converting a Number to a String

age = 30  # An integer representing age
age_str = str(age)  # Convert to a string for text display
print(age_str, type(age_str))  # Output converted string and its type

4. Converting Values to Boolean

print(bool(0))  # False
print(bool(1))  # True, any non-zero number is 'True'
print(bool(""))  # False, an empty string is 'False'
print(bool("Hello"))  # True, non-empty strings are 'True'

If you notice, I am not overwriting variables. Instead, i am creating a new variable each time. That helps to avoid confusion when you need the same values of different types for varying reasons.

Quick Practice

Try these out to test what you’ve learned.

1️. Check the type of a variable

value = "42"  # A string containing numeric characters
print(value, type(value))  # Output value and its type

2️. Convert a string to a float and print it

num = "10.5"  # A string representation of a decimal number
num = float(num)  # Convert the string into a float
print(num, type(num))  # Output converted float and its type

3️. Try converting a boolean to an integer

boolean_value = True  # A boolean variable
int_value = int(boolean_value)  # Convert to integer
print(int_value, type(int_value))  # Output converted integer and its type

Summary

• Python has several built-in data types: strings, integers, floats, booleans, and NoneType.
• Use type() to check a variable’s data type/the kind of value you’re working with.
• Convert data types using int(), float(), str(), and bool().

Next, we will introduce data structures in Python, starting with lists and dictionaries.

Recommended Python Books

• Fluent Python: Clear, Concise, and Effective Programming
• Practical Statistics for Data Scientists: 50+ Essential Concepts Using R and Python
• Python for Data Analysis: Data Wrangling with pandas, NumPy, and Jupyter
• Learning Python: Powerful Object-Oriented Programming
• Python Crash Course
• Python Programming for Beginners
• Pandas Cookbook