Avanceret Aritmetik
Learn how Python handles floor division and modulo (including negative numbers) and explore the math module for common numeric operations.
Floor Division (//)
Returns the floor of the exact quotient, meaning it rounds the result down.
12print(7 // 3) # 2 print(-7 // 3) # -3 (floors down: -2.333... → -3)
Why it matters: indexing chunks/pages, time splitting (hours from seconds), and any "how many full groups fit" calculation.
Modulo %
Returns the remainder of division. In Python, the remainder always has the same sign as the divisor.
123print(7 % 3) # 1 print(-7 % 3) # 2 print(7 % -3) # -2
Why it matters: "every Nth" item, wrap-around (e.g., clock arithmetic), cycling through buckets.
Examples:
- Keeping track of hours on a clock →
14 % 12 = 2- (2 PM); - Selecting every 3rd item in a list →
if i % 3 == 0:.
Quick Note on Rounding
Built-in round(x, ndigits) uses "round half to even".
12print(round(2.5), round(3.5)) # 2 4 print(round(2.675, 2)) # 2.67 (binary float nuance)
The math Module
Import once and access many handy functions/constants.
123456import math print(math.floor(2.9), math.ceil(2.1), math.trunc(-2.9)) # 2 3 -2 print(math.sqrt(9)) # 3.0 print(math.pi, math.e) # 3.14159... 2.71828... print(math.isfinite(1.0), math.isfinite(float('inf'))) # True False
1. What value will this code output?
2. What value will this code output?
3. Which call returns -3?
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Can you explain why the remainder has the same sign as the divisor in Python?
What are some practical examples of using floor division and modulo together?
Can you show more examples of using the math module functions?
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Learn how Python handles floor division and modulo (including negative numbers) and explore the math module for common numeric operations.
Floor Division (//)
Returns the floor of the exact quotient, meaning it rounds the result down.
12print(7 // 3) # 2 print(-7 // 3) # -3 (floors down: -2.333... → -3)
Why it matters: indexing chunks/pages, time splitting (hours from seconds), and any "how many full groups fit" calculation.
Modulo %
Returns the remainder of division. In Python, the remainder always has the same sign as the divisor.
123print(7 % 3) # 1 print(-7 % 3) # 2 print(7 % -3) # -2
Why it matters: "every Nth" item, wrap-around (e.g., clock arithmetic), cycling through buckets.
Examples:
- Keeping track of hours on a clock →
14 % 12 = 2- (2 PM); - Selecting every 3rd item in a list →
if i % 3 == 0:.
Quick Note on Rounding
Built-in round(x, ndigits) uses "round half to even".
12print(round(2.5), round(3.5)) # 2 4 print(round(2.675, 2)) # 2.67 (binary float nuance)
The math Module
Import once and access many handy functions/constants.
123456import math print(math.floor(2.9), math.ceil(2.1), math.trunc(-2.9)) # 2 3 -2 print(math.sqrt(9)) # 3.0 print(math.pi, math.e) # 3.14159... 2.71828... print(math.isfinite(1.0), math.isfinite(float('inf'))) # True False
1. What value will this code output?
2. What value will this code output?
3. Which call returns -3?
Tak for dine kommentarer!
