mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-11-30 16:31:08 +00:00
0e7f8284a3
* Add error tests in doctest and fix error message * Change AssertationError to ValueError * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci --------- Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
91 lines
2.2 KiB
Python
91 lines
2.2 KiB
Python
"""Prime Check."""
|
|
|
|
import math
|
|
import unittest
|
|
|
|
import pytest
|
|
|
|
|
|
def is_prime(number: int) -> bool:
|
|
"""Checks to see if a number is a prime in O(sqrt(n)).
|
|
|
|
A number is prime if it has exactly two factors: 1 and itself.
|
|
|
|
>>> is_prime(0)
|
|
False
|
|
>>> is_prime(1)
|
|
False
|
|
>>> is_prime(2)
|
|
True
|
|
>>> is_prime(3)
|
|
True
|
|
>>> is_prime(27)
|
|
False
|
|
>>> is_prime(87)
|
|
False
|
|
>>> is_prime(563)
|
|
True
|
|
>>> is_prime(2999)
|
|
True
|
|
>>> is_prime(67483)
|
|
False
|
|
>>> is_prime(16.1)
|
|
Traceback (most recent call last):
|
|
...
|
|
ValueError: is_prime() only accepts positive integers
|
|
>>> is_prime(-4)
|
|
Traceback (most recent call last):
|
|
...
|
|
ValueError: is_prime() only accepts positive integers
|
|
"""
|
|
|
|
# precondition
|
|
if not isinstance(number, int) or not number >= 0:
|
|
raise ValueError("is_prime() only accepts positive integers")
|
|
|
|
if 1 < number < 4:
|
|
# 2 and 3 are primes
|
|
return True
|
|
elif number < 2 or number % 2 == 0 or number % 3 == 0:
|
|
# Negatives, 0, 1, all even numbers, all multiples of 3 are not primes
|
|
return False
|
|
|
|
# All primes number are in format of 6k +/- 1
|
|
for i in range(5, int(math.sqrt(number) + 1), 6):
|
|
if number % i == 0 or number % (i + 2) == 0:
|
|
return False
|
|
return True
|
|
|
|
|
|
class Test(unittest.TestCase):
|
|
def test_primes(self):
|
|
assert is_prime(2)
|
|
assert is_prime(3)
|
|
assert is_prime(5)
|
|
assert is_prime(7)
|
|
assert is_prime(11)
|
|
assert is_prime(13)
|
|
assert is_prime(17)
|
|
assert is_prime(19)
|
|
assert is_prime(23)
|
|
assert is_prime(29)
|
|
|
|
def test_not_primes(self):
|
|
with pytest.raises(ValueError):
|
|
is_prime(-19)
|
|
assert not is_prime(
|
|
0
|
|
), "Zero doesn't have any positive factors, primes must have exactly two."
|
|
assert not is_prime(
|
|
1
|
|
), "One only has 1 positive factor, primes must have exactly two."
|
|
assert not is_prime(2 * 2)
|
|
assert not is_prime(2 * 3)
|
|
assert not is_prime(3 * 3)
|
|
assert not is_prime(3 * 5)
|
|
assert not is_prime(3 * 5 * 7)
|
|
|
|
|
|
if __name__ == "__main__":
|
|
unittest.main()
|