Learn How to Write Python Code with Whole Numbers: Absolute Beginners Tutorial

Whole numbers are the foundation of nearly every Python program you will write. Whether you are counting items in a list, tracking a player's score, or calculating the number of seconds in a day, you are working with integers. This tutorial walks through everything an absolute beginner needs to know about Python's int type, from creating your first integer variable to performing arithmetic and converting between types.

Every programming language has a way of representing whole numbers, but Python handles them in a way that is especially friendly to beginners. You never have to declare a type, you never have to worry about size limits, and the syntax reads almost like plain English. By the end of this tutorial, you will be comfortable creating integer variables, doing math with them, and avoiding the common mistakes that trip up newcomers.

What Is an Integer in Python?

An integer is a whole number with no decimal point. It can be positive, negative, or zero. In Python, integers are represented by the int type, and you create one simply by assigning a whole number to a variable.

age = 25
temperature = -7
zero = 0
large_number = 1_000_000

print(type(age))          # <class 'int'>
print(type(temperature))  # <class 'int'>
print(large_number)       # 1000000

Notice that 1_000_000 uses underscores as visual separators. Python ignores these underscores entirely, so the value is identical to 1000000. This is a readability feature introduced in Python 3.6 that makes large numbers much easier to scan at a glance.

Integers vs. Floats: The Decimal Point Matters

The presence of a decimal point is what separates an integer from a float. The number 10 is an int, but 10.0 is a float. This distinction matters because it affects the type of your variable, and mixing types can produce unexpected results if you are not paying attention.

whole = 10
decimal = 10.0

print(type(whole))    # <class 'int'>
print(type(decimal))  # <class 'float'>
print(whole == decimal)  # True (same value, different types)

Python considers 10 and 10.0 equal in value, but they are different types under the hood. This matters when you need strict type checking or when the result of an operation depends on the type of the input.

Arithmetic Operators for Whole Numbers

Python provides a full set of arithmetic operators that work naturally with integers. If you have ever used a calculator, you already know how addition, subtraction, and multiplication work. Python adds a few extras that are especially useful for programming.

Here is a practical example that combines several operators to calculate how many full weeks and leftover days fit into a given number of days.

total_days = 100

weeks = total_days // 7
leftover = total_days % 7

print(f"{total_days} days = {weeks} weeks and {leftover} days")
# 100 days = 14 weeks and 2 days

Converting Between Types with int()

Python's built-in int() function converts other data types into integers. This is essential when reading user input (which arrives as a string) or when you need to strip the decimal portion from a float.

# Converting a string to an integer
user_input = "42"
number = int(user_input)
print(number + 8)  # 50

# Converting a float to an integer (truncates toward zero)
price = 9.99
whole_price = int(price)
print(whole_price)  # 9

# Negative float truncation
neg = -3.7
print(int(neg))  # -3 (truncates toward zero, not down)

Checking a Value's Type

When you are unsure whether a variable holds an integer, use isinstance() or type() to inspect it.

value = 42

print(type(value))              # <class 'int'>
print(isinstance(value, int))   # True
print(isinstance(value, float)) # False

The isinstance() function is generally preferred over type() checks because it handles subclasses correctly. In Python, bool is a subclass of int, so isinstance(True, int) returns True. This reflects how Python treats booleans as a special case of integers, where True equals 1 and False equals 0.

Python Learning Summary Points

1. Integers in Python are whole numbers with no decimal point, represented by the int type. You create them by assigning a number like 42 or -7 to a variable.
2. Python integers have arbitrary precision and no fixed size limit. A Python int can grow as large as available memory allows, unlike integers in C or Java.
3. The / operator always returns a float, even when dividing two integers evenly. Use // for floor division when you need an integer result.
4. The int() function converts strings and floats into integers. Float-to-int conversion truncates toward zero, and non-numeric strings will raise a ValueError.
5. Use isinstance(value, int) to check whether a variable is an integer. This approach correctly handles subclasses like bool.

Whole numbers are one of the first building blocks you will use in Python, and they stay relevant at every skill level. From simple counters to complex algorithms, the int type underpins an enormous range of programming tasks. Practice the examples in this tutorial, try the interactive challenges, and experiment in your own Python environment to build confidence with integers before moving on to more advanced data types.