Question

For problem set 1 question 1, I'm trying to build a program that prompts the user for a desired prime, then finds and prints that prime.

From what I can tell, the list of primes isn't getting built, but I can't figure out why. Any ideas? Thanks in advance!

Answer 1

here's my code:


inputnumprime = raw_input("Which prime would you like? i.e. for the third prime, enter 3.") #creates stopping point based on user entry
inputnumprime = int(inputnumprime) #conver the user input from a string to an integer
if inputnumprime == 1:
print 2
else:
primes = [] #creates empty list of primes
count = 2 #starts count at 1 to include the number 2
primecandidate = 3 #starts at first possible prime after 2
numbers = range(0, primecandidate) #creates list of possible numbers
while (count<(inputnumprime)): #run the test as long as we haven't reached the prime that the user is looking for
for divisor in range(2,(int(primecandidate**0.5) + 1),2): #dynamically creates a list of factors to test
if primecandidate%divisor==0: #is the prime candidate divisible by any of the factors?
primecandidate = primecandidate + 2 #if so, increase the candidate by 2 to get to the next odd number
else:
list.append(primes) #otherwise, add it to the list of primes and
count = count + 1 #and increase the count
primecandidate = primecandidate + 2 #and increase the candidate by 2 to try the next one
print primes[-1] #print the last prime number to tell the user their desired prime

Answer 2

i would start out with an empty list or a tuple such as primes = ()
then find out if a range of numbers are odd or even, if odd find out if they are prime numbers.
just keep breaking these down, like if they're odd and less than 9 you know its a prime so just go ahead and print those, if it's odd and greater than 9 find out if it is prime.
(all of this can be done in one for statement btw)
that's how i did mine anyways

Answer 3

Try this:
#Problem Set 1 - Problem 1
#Name: Username53
#Collaborators: None
#Time: 2 days

n = int(raw_input("Which Prime do you want? "))

counter = 1
prime = 3
total = n

while (counter < total):
divisor = prime/2
while (divisor > 1):
if prime % divisor == 0:
prime = prime + 2
divisor = prime / 2
else: divisor = divisor - 1
counter = counter + 1
prime = prime + 2
print prime - 2