diff --git a/maths/twin_prime.py b/maths/twin_prime.py new file mode 100644 index 000000000..e6ac0cc78 --- /dev/null +++ b/maths/twin_prime.py @@ -0,0 +1,45 @@ +""" +== Twin Prime == +A number n+2 is said to be a Twin prime of number n if +both n and n+2 are prime. + +Examples of Twin pairs: (3, 5), (5, 7), (11, 13), (17, 19), (29, 31), (41, 43), ... +https://en.wikipedia.org/wiki/Twin_prime +""" + +# Author : Akshay Dubey (https://github.com/itsAkshayDubey) +from maths.prime_check import is_prime + + +def twin_prime(number: int) -> int: + """ + # doctest: +NORMALIZE_WHITESPACE + This functions takes an integer number as input. + returns n+2 if n and n+2 are prime numbers and -1 otherwise. + >>> twin_prime(3) + 5 + >>> twin_prime(4) + -1 + >>> twin_prime(5) + 7 + >>> twin_prime(17) + 19 + >>> twin_prime(0) + -1 + >>> twin_prime(6.0) + Traceback (most recent call last): + ... + TypeError: Input value of [number=6.0] must be an integer + """ + if not isinstance(number, int): + raise TypeError(f"Input value of [number={number}] must be an integer") + if is_prime(number) and is_prime(number + 2): + return number + 2 + else: + return -1 + + +if __name__ == "__main__": + import doctest + + doctest.testmod()