'While' question

[Ben Keshet]

Thanks.  I tried to use 'for' instead of 'while' as both of you 
suggested.  It's running well as my previous version but breaks 
completely instead of just skipping the empty file.  I suspect the 
reason is that this part is inside another 'for' so it stops 
everything.  I just want to it to break only one 'for', that is go back 
to 5th line in the example code (directory C has one empty file):

receptors = ['A', 'B', 'C']
for x in receptors:
   print x
   for i in range(3):
       for r in (7, 9, 11, 13, 15, 17):
           f = 
open('c:/Linux/Dock_method_validation/%s/validation/ligand_ran_line_%s_%sA_secondary_scored.mol2' 
%(x,i,r), 'r')
           line = f.readline()[:-1]
           out_file = 
open('c:/Linux/Dock_method_validation/%s/validation/pockets.out' %(x),'a')
           out_file.write('%s ' %i)
           out_file.write('%s ' %r)
           # skip to scores
           j=0
           for line in f:
               line = line.rstrip()
               if "PRIMARY" not in line:
                   j += 1
                   if j == 20:
                       break
               else:
                   for line in f:
                       if "TRIPOS" not in line:
                           line = line.rstrip()
                           out_file.write(line)
                       else:
                           break
           f.close()
           out_file.close()

Any suggestions as for how to control the "extent of break"? should I do 
something else instead?  Thank you!