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* 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."""
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import math
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import unittest
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import pytest
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def is_prime(number: int) -> bool:
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"""Checks to see if a number is a prime in O(sqrt(n)).
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A number is prime if it has exactly two factors: 1 and itself.
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>>> is_prime(0)
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False
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>>> is_prime(1)
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False
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>>> is_prime(2)
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True
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>>> is_prime(3)
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True
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>>> is_prime(27)
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False
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>>> is_prime(87)
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False
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>>> is_prime(563)
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True
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>>> is_prime(2999)
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True
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>>> is_prime(67483)
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False
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>>> is_prime(16.1)
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Traceback (most recent call last):
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...
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ValueError: is_prime() only accepts positive integers
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>>> is_prime(-4)
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Traceback (most recent call last):
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...
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ValueError: is_prime() only accepts positive integers
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"""
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# precondition
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if not isinstance(number, int) or not number >= 0:
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raise ValueError("is_prime() only accepts positive integers")
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if 1 < number < 4:
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# 2 and 3 are primes
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return True
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elif number < 2 or number % 2 == 0 or number % 3 == 0:
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# Negatives, 0, 1, all even numbers, all multiples of 3 are not primes
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return False
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# All primes number are in format of 6k +/- 1
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for i in range(5, int(math.sqrt(number) + 1), 6):
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if number % i == 0 or number % (i + 2) == 0:
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return False
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return True
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class Test(unittest.TestCase):
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def test_primes(self):
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assert is_prime(2)
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assert is_prime(3)
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assert is_prime(5)
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assert is_prime(7)
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assert is_prime(11)
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assert is_prime(13)
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assert is_prime(17)
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assert is_prime(19)
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assert is_prime(23)
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assert is_prime(29)
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def test_not_primes(self):
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with pytest.raises(ValueError):
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is_prime(-19)
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assert not is_prime(
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0
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), "Zero doesn't have any positive factors, primes must have exactly two."
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assert not is_prime(
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1
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), "One only has 1 positive factor, primes must have exactly two."
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assert not is_prime(2 * 2)
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assert not is_prime(2 * 3)
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assert not is_prime(3 * 3)
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assert not is_prime(3 * 5)
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assert not is_prime(3 * 5 * 7)
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if __name__ == "__main__":
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unittest.main()
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