Too many values problem

Question

Hi , i was trying to make a full lot of ips for testing using this code :

ip_is = [i for i in range(256)]
ports = [i for i in range(1024,49152)]
return [str(i1)+"."+str(i2)+"."+str(i3)+"."+str(i4)+":"+str(p) for i1,i2,i3,i4,port in ip_is,ip_is,ip_is,ip_is,ports]

The problem is the 3rd line in which is made the ip list. If there is a way to make it all at once or how can make one at time in a lazy way ? I'm pretty noob at python :P.

Thanks for the Help :)

Answer 1

You should use a generator instead of creating the full list:

def all_addresses():
   ip_is = [i for i in range(256)]
   ports = [i for i in range(1024,49152)]
   # note (...) instead of [...] to create a generator instead of a list;
   # separate |for|s to iterate over the lists individually
   return (str(i1)+"."+str(i2)+"."+str(i3)+"."+str(i4)+":"+str(p)
            for i1 in ip_is
            for i2 in ip_is
            for i3 in ip_is
            for i4 in ip_is
            for p in ports)

for addr in all_addresses():
   print addr

This way you will not run out of memory, but it will still take a very, very long time to iterate through all these addresses.

Answer 2

return ('%d.%d.%d.%d:%d' % (i1, i2, i3, i4, port) for i1, i2, i3, i4, port in itertools.product(ip_is, ip_is, ip_is, ip_is, ports))

Answer 3

You're trying (quite apart from the syntax issues) to make a list of

256 * 256 * 256 * 256 * (49152 - 1024)

strings -- i.e., 206708186021888 strings... about two hundred thousand billions of strings.

If you made one per microsecond, that would take you 6.5 years (even quite apart from the problem of finding the petabytes of RAM to hold them).

I know you want to "make a full lot of ips for testing", but that's way too full a lot.

Why not take a random sample from this huge set, instead? E.g.:

import random

def random_address():
  ip = tuple(random.randrange(256) for i in range(4))
  port = random.randrange(1024, 49152)
  format = '.'.join(['%s'] * 4) + ':%s'
  return format % (ip + (port,))

now, if you want (e.g.) a million such strings for your testing, just do:

millionstrings = [random_address() for i in xrange(1000*1000)]