10 examples of 'python program to find prime numbers in a list' in Python

23
def findprimes(start, end):
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	for i in range(start, end):
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		if i not in Checked:
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			Checked.append(i)
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			if is_prime(i):
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				Primes.append(i)

12
def primes():
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    yield 2
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    yield 3
15
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    for i in itertools.count(start=5, step=2):
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        if is_prime(i):
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            yield i

20
def prime(num):
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    # num is actually a string because input() returns strings. We'll convert it to int
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    num = int(num)
23
24
    if num < 0:
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        print("Negative integers can not be prime")
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        quit()
27
    if num is 1:
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        print("1 is neither prime nor composite")
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        # See how I lazily terminated program otherwise it'd forward "None"(default behaviour of python when function
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        # returns nothing) rather than True or False. Which could mess up the program.
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        # If we hit this if statement above statement is printed then program exits.
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        quit()  # Now you don't need to get sys.exit() to exit python has quit to handle the same thing
33
    if num in [2, 3]:
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        # if given argument is 2 or 3, it is prime. We used list without defining a variable which is perfectly valid
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        return True
36
    if num % 2 == 0:  # excluding all even numbers except two.
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        return False
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    else:
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        # Here we are starting counter variable from 3 in range. Second argument excludes numbers above one third
40
        # of the given argument. Third argument in range sets steps to take to 2. This makes loop to iterate odds
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        for x in range(3, int(num/3), 2):
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            # Checking if argument is divisible by counter. % is modulus operator which returns remainder of division
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            if num % x == 0:
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                return False
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    # It's okay to have more than one return statement when program hits return statement it exits the function.
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    return True

7
def isPrime(num):
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    # Returns True if num is a prime number, otherwise False.
9
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    # Note: Generally, isPrime() is slower than primeSieve().
11
12
    # all numbers less than 2 are not prime
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    if num < 2:
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        return False
15
16
    # see if num is divisible by any number up to the square root of num
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    for i in range(2, int(math.sqrt(num)) + 1):
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        if num % i == 0:
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            return False
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    return True

7
def prime():
8
    D = {9: 3, 25: 5}
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    yield 2
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    yield 3
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    yield 5
12
    MASK = 1, 0, 1, 1, 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0,
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    MODULOS = frozenset((1, 7, 11, 13, 17, 19, 23, 29))
14
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    for q in it.compress(
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            it.islice(it.count(7), 0, None, 2),
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            it.cycle(MASK)):
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        p = D.pop(q, None)
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        if p is None:
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            D[q * q] = q
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            yield q
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        else:
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            x = q + 2 * p
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            while x in D or (x % 30) not in MODULOS:
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                x += 2 * p
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            D[x] = p

746
def prime_number_factorisation(n):
747
    if n < 2:
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        return [n]
749
    i = 2
750
    factors = []
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    while i * i <= n:
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        if n % i:
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            i += 1
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        else:
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            n //= i
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            factors.append(i)
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    if n > 1:
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        factors.append(n)
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    return factors

12
def isprime(n):
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    n = int(n)
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    return n > 1 and all(n%i for i in islice(count(2), int(sqrt(n)-1)))

50
def prime_factors(n):
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    """Lists prime factors of a given natural integer, from greatest to smallest
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    :param n: Natural integer
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    :rtype : list of all prime factors of the given natural n
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    """
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    i = 2
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    while i <= sqrt(n):
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        if n % i == 0:
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            l = prime_factors(n/i)
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            l.append(i)
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            return l
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        i += 1
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    return [n]      # n is prime

6
def is_prime(n):
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   '''
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   checks if a number is prime
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   '''
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   if n < 2:
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      return False
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   if n == 2:
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      return True
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   for x in range(2, int(n**0.5)+1, 2):
15
      if n % x == 0:
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         return False
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   return True

36
def primes_from(prime_sieve):
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    for n, is_prime in enumerate(prime_sieve):
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        if is_prime:
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            yield n