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How to Filter Even Numbers and Square Them in Python
Create two beginner-friendly helper functions that filter even numbers and compute squares of a number list using loops, then print the results along with the sum and average.
def get_even_numbers(numbers):
evens = []
for num in numbers:
if num % 2 == 0:
evens.append(num)
return evens
def get_squares(numbers):
squares = []
for num in numbers:
squares.append(num ** 2)
return squares
numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
even_numbers …Mutual Recursion for Even/Odd Check in Python
Implements even and odd checks using two functions that call each other recursively, demonstrating base cases and alternating calls.
def is_even(n):
if n == 0:
return True
return is_odd(n - 1)
def is_odd(n):
if n == 0:
return False
return is_even(n - 1)
if __name__ == "__main__":
for num in range(0, 11):
print(f"{num}: even={is_even(num)}, odd={is_odd(num)}")Compound interest calculator in Python
Compute future investment value with the compound interest formula and a readable year-by-year loop.
def future_value(
principal: float,
annual_rate: float,
years: int,
compounds_per_year: int = 12,
) -> float:
"""Return balance after compound interest (rounded to cents)."""
rate_per_period = annual_rate / compounds_per_year
periods = compounds_per_year * years
amount = principal * (1 …How to Assert an Invariant After a Complex Transformation in Python
Use assert to verify that a multi-step transformation preserves a mathematical invariant, catching regressions early.
def transform_value(value):
"""Apply several transformations to a value."""
doubled = value * 2
shifted = doubled + 10
normalized = shifted / 2
return int(normalized)
def assert_invariant(value):
"""Assert that the transformation preserves a key invariant."""
original = value
transform…Binary Search on Answer in Python: Koko Eating Bananas
Find the minimum eating speed so Koko finishes all banana piles within a given hour limit using binary search on the answer.
import math
def min_eating_speed(piles, h):
"""Return minimum integer eating speed K so Koko finishes within h hours."""
def hours_needed(speed):
return sum(math.ceil(p / speed) for p in piles)
low, high = 1, max(piles)
while low < high:
mid = (low + high) // 2
if hours_needed…How to Compute Cosine Similarity Between Two Vectors in Python
This code calculates the cosine similarity between two numeric vectors using the dot product and Euclidean norms, returning a value between -1 and 1.
import math
def cosine_similarity(vec_a, vec_b):
if len(vec_a) != len(vec_b):
raise ValueError("Vectors must have the same length")
dot_product = sum(a * b for a, b in zip(vec_a, vec_b))
norm_a = math.sqrt(sum(a * a for a in vec_a))
norm_b = math.sqrt(sum(b * b for b in vec_b))
i…How to Generate an Arithmetic Progression List in Python
Generates a list of terms in an arithmetic progression using a list comprehension.
def generate_ap(start, difference, count):
"""Generate a list of n terms in an arithmetic progression."""
return [start + i * difference for i in range(count)]
if __name__ == "__main__":
ap = generate_ap(3, 5, 6)
print(ap)How to Generate Primes with a Generator in Python
Generate prime numbers up to a limit using the Sieve of Eratosthenes wrapped in a generator expression for lazy evaluation.
def prime_generator(limit):
sieve = [True] * (limit + 1)
sieve[0] = sieve[1] = False
for i in range(2, int(limit ** 0.5) + 1):
if sieve[i]:
for j in range(i * i, limit + 1, i):
sieve[j] = False
return (num for num, is_prime in enumerate(sieve) if is_prime)
if __n…How to Generate a Collatz Sequence in Python
Generate the Collatz sequence for a given positive integer by repeatedly applying the 3n+1 rule until reaching 1.
def collatz_sequence(n):
if n <= 0:
raise ValueError("n must be a positive integer")
sequence = [n]
while n != 1:
if n % 2 == 0:
n = n // 2
else:
n = 3 * n + 1
sequence.append(n)
return sequence
if __name__ == "__main__":
start = 7
result…Fix and Test a Regression Bug in Python with Unit Tests
This code implements a circle area function that raises ValueError for negative radii, then runs basic tests and a regression check for that edge case.
import math
def calculate_area(radius):
"""Calculate the area of a circle given its radius."""
if radius < 0:
raise ValueError("Radius cannot be negative")
return math.pi * radius ** 2
def main():
test_cases = [0, 1, 2.5, 5, 10]
print("Circle Area Calculator")
print("-" * 30)
…How to Run a Fisher Exact Test in Python
Compute the two-sided Fisher exact test p-value for a 2x2 contingency table using pure Python and the math module.
from math import comb, factorial
from itertools import combinations
def hypergeometric_probability(a, b, c, d):
"""Probability of observing table [[a, b], [c, d]] under the null."""
row1 = a + b
row2 = c + d
col1 = a + c
col2 = b + d
total = row1 + row2
return (comb(row1, a) * comb(row2, …Browse by section
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