- Download list of prime numbers how to#
- Download list of prime numbers generator#
- Download list of prime numbers code#
There are 25 prime numbers between 1 and 100.
Download list of prime numbers how to#
How to work out if a number is a prime number or not. 13 ÷ 6 = 2 remainder 1.ġ5 is not an example of a prime number because it can be divided by 5 and 3 as well as by itself and 1.ġ5 is an example of a composite number because it has more than two factors. Dividing a prime number by another number results in numbers left over e.g.
What is a prime number?Ī prime number is a number greater than 1 with only two factors – themselves and 1.Ī prime number cannot be divided by any other numbers without leaving a remainder.Īn example of a prime number is 13. Here we explain what exactly this means, give you a list of the prime numbers children need to know at primary school and provide you with some practice prime number questions and examples. This works, but I am always open to better ways to make is_prime function.A prime number is a number that can only be divided by itself and 1 without remainders.
Download list of prime numbers generator#
So I can see that we have right answers for different questions here for a prime number generator gen_primes looks like the right answer but for a prime number check, the simple_is_prime function is better suited.
Download list of prime numbers code#
The result of running this code show interesting results: $ python prime_time.py Setup="from _main_ import simple_is_prime", Setup="from _main_ import regex_is_prime", Setup="from _main_ import oneliner_is_prime", Setup="from _main_ import simple_gen_primes", Less1000primes = list(gen_primes(limit=1000))Īssert less1000primes = list(simple_gen_primes(limit=1000)) """Prime number generator based on simple gen""" More efficient than oneliner_is_prime as it breaks the loop While limit is None or num 1 and list(gen_primes(limit=num)).pop() = num Just studied the topic, look for the examples in the thread and try to make my version: from collections import defaultdict """Make number odd by adding one to it if it was even, otherwise return it unchanged""" """Test whether number is evenly divisable by odd divisor."""įor divisor in xrange(3, maxDivisor + 1, 2): Return itertools.chain(prefix, prime_generator) Prime_generator = (num for num in odd_numbers if not has_odd_divisor(num)) Odd_numbers = (num for num in xrange(odd_rfrom, rto + 1, 2)) Odd_rfrom = 3 if rfrom < 3 else make_odd(rfrom) # make rfrom an odd number so that we can skip all even nubers when searching for primes, also skip 1 as a non prime odd number. Prefix = if rfrom 1 else # include 2 if it is in range separately as it is a "weird" case of even prime """Create iterator of prime numbers in range """ Usage: primes = list(create_prime_iterator(1, 30)) import math Everything done with lazy streams (python generators). Sieve.primerange(a, b) # Generate all prime numbers in the range [a, b), implemented as a dynamically growing sieve of Eratosthenes.Īnother simple example, with a simple optimization of only considering odd numbers. Nextprime(n) # Return the ith prime greater than n Prevprime(n, ith=1) # Return the largest prime smaller than n The nth prime is approximately n*log(n) and can never be larger than 2**n.
Prime(nth) # Return the nth prime, with the primes indexed as prime(1) = 2. Primepi(n) # Return the number of prime numbers less than or equal to n. Randprime(a, b) # Return a random prime number in the range [a, b). Primerange(a, b) # Generate a list of all prime numbers in the range [a, b). isprime(n) # Test if n is a prime number (True) or not (False). It provides several functions to generate prime numbers. SymPy is a Python library for symbolic mathematics. # multiples of its witnesses to prepare for larger # need it in the map, but we'll mark the next # Yield it and mark its first multiple that isn't # The running integer that's checked for primeness # indefinitely, but only as long as required by the current # This is memory efficient, as the sieve is not "run forward" # Maps composites to primes witnessing their compositeness. """ Generate an infinite sequence of prime numbers. Here's a nice, optimized implementation with many comments: # Sieve of Eratosthenes Here's your code with a few fixes, it prints out only primes: import mathįor x in range(2, int(math.sqrt(count) + 1)):įor much more efficient prime generation, see the Sieve of Eratosthenes, as others have suggested. continue moves to the next loop iteration - but you really want to stop it using break.Why do you print out count when it didn't divide by x? It doesn't mean it's prime, it means only that this particular x doesn't divide it.
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