Python's resultant issues

I'm new of Python and i'm stuck on this. I need to check if i can find a string in a file. I have created the file ContEAN.py

the code:

import sys

for arg in sys.argv:
inputEAN=arg
EAN = open("/home/master/Documenti/Progetti/eanFZ.txt","r")

riga=EAN.readlines()

EAN.close()

print inputEAN

for i in range(len(riga)):
if inputEAN == riga[i]:
    print "OK"

From Command line:

$ python ContEAN.py 455

where "455" will be the value of inputEAN

and this is the content of eanFZ.txt:

7777
777
0000000000156
0000000015
455
9999
85485
656565

the problem is that i never have an ok as ultimate result and i don't know why...