last2.py

def get_last_lines(fp, num, step=10):
    pos = step
    lines = []
    quit = False
    while len(lines) < num + 1 and not quit:
        fp.seek(-pos, 2)
        if int(fp.tell()) == 0:
            quit = True

        lines = fp.readlines()
        pos = pos + step
    return lines[-num:]


import unittest
from StringIO import StringIO

class TestGetLastLines(unittest.TestCase):
    def setUp(self):
        self.fp = StringIO("line1\nline2\nline3\n")

    def test_get(self):
        # jeden
        self.assertEqual(get_last_lines(self.fp, 1), ['line3\n'])

        # dva riadky
        self.assertEqual(
            get_last_lines(self.fp, 2),
            ['line2\n', 'line3\n'])
        
        # sto
        self.assertEqual(
            get_last_lines(self.fp, 100),
            ['line1\n', 'line2\n', 'line3\n'])

if __name__ == '__main__':
        unittest.main()






$ python last2.py 
.
----------------------------------------------------------------------
Ran 1 test in 0.000s