What Does `//` Mean in Python? (With Examples)
The double slash operator in Python performs floor division, rounding results down to the nearest integer. See how it handles floats, loops, and pagination.
In Python, // is the floor division operator. It divides two numbers and rounds the result down to the nearest whole number.
For example:
print(10 // 3) # Output: 3
print(-10 // 3) # Output: -4Key Takeaways
//performs floor division, meaning it rounds down the result.- Works with integers and floating-point numbers.
- Always rounds towards negative infinity (
-∞).
Understanding Floor Division (//)
The // operator divides two numbers but instead of returning a floating-point result, it truncates (rounds down) to the nearest integer.
Example:
print(7 // 2) # Output: 3 (instead of 3.5)
print(-7 // 2) # Output: -4 (rounds towards -∞)How Does // Handle Floats?
Even if one of the operands is a float, the result remains floored but in float format:
print(7.0 // 2) # Output: 3.0
print(-7.5 // 2) # Output: -4.0Difference Between / and //
Operator Description Example / Normal division (returns float) 5 / 2 = 2.5 // Floor division (rounds down) 5 // 2 = 2
When to Use //?
- When you only need whole numbers (e.g., counting items).
- Avoiding float precision errors (e.g., indexing arrays).
- Ensuring integer results in loops.
Example: Using // for pagination:
items_per_page = 10
total_items = 95
pages = total_items // items_per_page
print(pages) # Output: 9FAQs
Does `//` always return an integer?
No, if one of the operands is a float, the result is a float.
Why does `-10 // 3` return `-4` instead of `-3`?
Because `//` rounds towards negative infinity (`-∞`).
Is `//` the same as `math.floor(a / b)`?
Yes, `a // b` is equivalent to `math.floor(a / b)`.
Conclusion
The // operator in Python performs floor division, rounding the result down to the nearest whole number. It’s useful when working with integer math, loops, and pagination.
