An integer (int) is Python's built-in type for whole numbers of arbitrary size, with no fixed maximum like the fixed-width integers in many other languages.

Syntax

x = 42
y = -17
z = 0x1A  # hexadecimal
w = 0b101  # binary

Deep Dive Course

Python's int type has arbitrary precision — it automatically grows to hold numbers as large as memory allows, so there's no integer overflow the way there is in C or Java. Integer literals can be written in decimal, or with 0x/0o/0b prefixes for hexadecimal, octal, and binary. Division between two ints with / always returns a float, while // performs floor division and keeps an int result when both operands are ints.

1Understanding Integers

💡

Use // (floor division) when you specifically need an integer result, and % to get the remainder — together they implement the classic divmod relationship.

editor.html

a = 17
b = 5
print(a // b)
print(a % b)
print(a / b)

localhost:3000

2Practical Example

Here is a real-world application of Integers showing how it is used in production Python code.

editor.html

big = 2 ** 100
print(big)
print(type(big))

localhost:3000

3Best Practices

Follow these guidelines when working with Integers:

1. Use // for integer division instead of converting the result of / with int(), since int() truncates toward zero while // floors, which differs for negative numbers

2. Use underscores in large integer literals for readability, e.g. 1_000_000

3. Rely on Python's arbitrary-precision integers for exact big-number math instead of reaching for a third-party library

⚠️

Tip: Use // (floor division) when you specifically need an integer result, and % to get the remainder — together they implement the classic divmod relationship.

editor.html

a = 17
b = 5
print(a // b)
print(a % b)
print(a / b)

localhost:3000

Examples

Example 01Basic Usage

a = 17
b = 5
print(a // b)
print(a % b)
print(a / b)

Example 02Advanced Example

big = 2 ** 100
print(big)
print(type(big))

Best Practices

Use // for integer division instead of converting the result of / with int(), since int() truncates toward zero while // floors, which differs for negative numbers
Use underscores in large integer literals for readability, e.g. 1_000_000
Rely on Python's arbitrary-precision integers for exact big-number math instead of reaching for a third-party library

Interview Question

Why can Python integers grow to represent arbitrarily large numbers, unlike a fixed 32-bit or 64-bit int in C?▼

Hint: Think about how CPython actually stores an int in memory.

CPython implements int as a variable-length structure that stores its digits in an array, growing that array as needed, rather than a fixed-width machine word. This means arithmetic on very large integers costs more time and memory as they grow, but there's no fixed ceiling and no silent overflow — Python simply allocates more space when a number no longer fits.

Exercises

MediumPractice using Integers in a real scenario.

View Solution

a = 17
b = 5
print(a // b)
print(a % b)
print(a / b)

Frequently Asked Questions

Why can Python integers grow to represent arbitrarily large numbers, unlike a fixed 32-bit or 64-bit int in C?▼

Related Functions

floatsfloor divisiondivmod()