Question

I want to create a module that checks whether a number is prime or not, and to list all of the primes before it.

The functions in the module would take a bit of time if it had to generate the list of primes every single time it was created.

How do I open a .txt file that is in the same folder as the program is in, then have it access the data from it and create a list based off of that? The .txt file will be saved a list afterwards when the function is completed. I also need a bit of guidance on how to actually save the file in a given location.

Any suggestions or tips would be great. Thanks!

Answer 1

I would pickle a set object, you could do this:

import cPickle as pickle

primes_set = set([2,3,5])

pickle.dump(primes_set, open('primes_set.pkl', 'wb')) 

my_primes = pickle.load(open('primes_set.pkl', 'rb')) # to load the object

After you created a pickle file, you could use it like this:

def get_primes(my_nums):
    '''
    Return only prime numbers from inputted list.
    '''
    my_primes = pickle.load(open('primes_set.pkl', 'rb'))
    return [num for num in my_nums if num in my_primes]