TheAlgorithms_Python/maths/prime_check.py at problem_122 · mindaugl/TheAlgorithms_Python · GitHub

Name: TheAlgorithms_Python/maths/prime_check.py at problem_122 · mindaugl/TheAlgorithms_Python · GitHub
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"""Prime Check."""

importmath
importunittest

importpytest


defis_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
ifnotisinstance(number, int) ornotnumber>=0:
raiseValueError("is_prime() only accepts positive integers")

if1<number<4:
# 2 and 3 are primes
returnTrue
elifnumber<2ornumber%2==0ornumber%3==0:
# Negatives, 0, 1, all even numbers, all multiples of 3 are not primes
returnFalse

# All primes number are in format of 6k +/- 1
foriinrange(5, int(math.sqrt(number) +1), 6):
ifnumber%i==0ornumber% (i+2) ==0:
returnFalse
returnTrue


classTest(unittest.TestCase):
deftest_primes(self):
assertis_prime(2)
assertis_prime(3)
assertis_prime(5)
assertis_prime(7)
assertis_prime(11)
assertis_prime(13)
assertis_prime(17)
assertis_prime(19)
assertis_prime(23)
assertis_prime(29)

deftest_not_primes(self):
withpytest.raises(ValueError):
is_prime(-19)
assertnotis_prime(0), (
"Zero doesn't have any positive factors, primes must have exactly two."
 )
assertnotis_prime(1), (
"One only has 1 positive factor, primes must have exactly two."
 )
assertnotis_prime(2*2)
assertnotis_prime(2*3)
assertnotis_prime(3*3)
assertnotis_prime(3*5)
assertnotis_prime(3*5*7)


if__name__=="__main__":
unittest.main()