Why do i need to assign variable to f.readlines() in order to get its length?
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if do:

    os.chdir(path)
    f = open(file,"r")

    lines = f.readlines()
    print "without assignment " + str(len(f.readlines()))
    print "with assigment     " + str(len(lines))

i would expect the output the be the same. But its not:

    without assignment 0
    with assigment     1268

why is this?