Python prime numbers

2014-02-01 Thread Panagiotis Anastasiou 
Hi i'm new in programming and in python and i have an assignment that i cant 
complete. I have to Write a Python program to compute and print the first 200 
prime numbers. The output must be formatted with a title and the prime numbers 
must be printed in 5 properly aligned columns . I have used this code so far :

numprimes = raw_input('Prime Numbers  ')
count = 0
potentialprime = 2

def primetest(potentialprime):
divisor = 2
while divisor = potentialprime:
if potentialprime == 2:
return True
elif potentialprime % divisor == 0:
return False
break
while potentialprime % divisor != 0:
if potentialprime - divisor  1:
divisor += 1
else:
return True

while count  int(numprimes):
if primetest(potentialprime) == True:
print potentialprime
count += 1
potentialprime += 1
else:
potentialprime += 1

but i get the result in a single column . How can i get it in 5 rows? Can 
someone help please
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: Python prime numbers

2014-02-01 Thread Larry Martell 
On Saturday, February 1, 2014, Panagiotis Anastasiou panas...@gmail.com
wrote:

 Hi i'm new in programming and in python and i have an assignment that i
 cant complete. I have to Write a Python program to compute and print the
 first 200 prime numbers. The output must be formatted with a title and the
 prime numbers must be printed in 5 properly aligned columns . I have used
 this code so far :

 numprimes = raw_input('Prime Numbers  ')
 count = 0
 potentialprime = 2

 def primetest(potentialprime):
 divisor = 2
 while divisor = potentialprime:
 if potentialprime == 2:
 return True
 elif potentialprime % divisor == 0:
 return False
 break
 while potentialprime % divisor != 0:
 if potentialprime - divisor  1:
 divisor += 1
 else:
 return True

 while count  int(numprimes):
 if primetest(potentialprime) == True:
 print potentialprime
 count += 1
 potentialprime += 1
 else:
 potentialprime += 1

 but i get the result in a single column . How can i get it in 5 rows? Can
 someone help please



If you put a comma at the end of the print statement it will suppress the
newline.
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: Python prime numbers

2014-02-01 Thread Wiktor 
On Sat, 1 Feb 2014 07:33:47 -0800 (PST), Panagiotis Anastasiou wrote:

 Hi i'm new in programming and in python and i have an assignment that
 i cant complete. I have to Write a Python program to compute and print the 
 first 200 prime numbers. The output must be formatted with a title and the 
 prime numbers must be printed in 5 properly aligned columns . I have used 
 this 
 code so far :

  Hi,
  try out this code:

for i in range(200):
   print '{0:5}'.format(i),
   if (i-4) % 5 == 0:
   print

  Or maybe, if it's still unclear, try execute these lines:

print 'Hello {0}'.format('world')
print '|{0:30}|'.format('right')
print '|{0:30}|'.format('left')
print '|{0:^30}|'.format('center')
print '|{0:16}|'.format('right'),
print '|{0:16}|'.format('left'),
print '|{0:^16}|'.format('center')

  But still, it might be hard to implement this printing for..in loop while
you're verifying primes (in another loop), so maybe think about getting first
200 primes in while loop like you do (and only storing them in a list), and
then printing them out from this list in external for..in loop.



  Now, to your primetest() function. It may be good for small primes, but try
to verify with it, if 832475734579 is a prime. :)

 def primetest(potentialprime):
 divisor = 2
 while divisor = potentialprime:

  First of all, see that you rarely use this loop - you check this condition at
most two times. You end up for good in the second while loop.

 if potentialprime == 2:
 return True
 elif potentialprime % divisor == 0:
 return False
 break

  'break' after return is redundant - never executes

 while potentialprime % divisor != 0:
 if potentialprime - divisor  1:
 divisor += 1
 else:
 return True

  So, this is your main loop. Very inefficient. Think about that:
a) do you really have to check divisors up to the potentialprime? 
   Maybe there is a point, where you may say, that you've checked all 
   possibilities? Remember that a * b = b * a 
b) do you really have to check every divisor? I mean, increasing 
   it by 1 in every step?

-- 
Best regards, Wiktor Matuszewski
'py{}@wu{}em.pl'.format('wkm', 'ka')
-- 
https://mail.python.org/mailman/listinfo/python-list