Python help (finding duplicates)

[Kevin Faulkner]

I was trying to pull duplicates out of 2 different files. Needless to say there 
are duplicates I would place a # next to the duplicate. Example files:
file 1:	file 2:
433.3	947.3
543.1	749.0
741.1	859.2
238.5	433.3
839.2	229.1
583.6	990.1
863.4	741.1
859.2	101.8

import string
i=1
primaryfile = open('/tmp/extract','r')
secondaryfile = open('/tmp/unload')
for line in primaryfile:
   pcompare = line
   print(pcompare)
   for row in secondaryfile:
     i = i + 1
     print(i)
     scompare = row
     if pcompare == scompare:
       print(scompare)
       secondaryfile.write('#')
With this code it should go through the files and find a duplicate and place a 
'#' next to it. But for some reasonson it doesn't even get to the second for 
statement. I don't know what else to do. Please offer some assistance. :)