Show the Feynman Point is the longest sequence in the first 100000 digits of py

longest_seq_pi.py

import unittest

class longest_seq:
    def find(sentence):
        pos = 0
        l = 0
        cl = 0
        cpos = 0
        i = 0
        t = ''
        while i < len(sentence):
            if t == sentence[i]:
                cl += 1
            else:
                if cl > l:
                    l = cl + 1
                    pos = cpos
                t = sentence[i]
                cl = 0
                cpos = i
            i += 1
        if cl > l:
            l = cl
            pos = cpos
        if l > 0:
            return (pos, sentence[pos], l)
        return None
        

class Testing(unittest.TestCase):
    def test_example1(self):
        result = longest_seq.find('abababaaaababab')
        self.assertEqual(6, result[0])
        self.assertEqual('a', result[1])
        self.assertEqual(4, result[2])

    def test_increasing(self):
        result = longest_seq.find('012333456789')
        self.assertEqual(3, result[0])
        self.assertEqual('3', result[1])
        self.assertEqual(3, result[2])

    def test_secondshorter(self):
        result = longest_seq.find('abababaaaabaabab')
        self.assertEqual(6, result[0])
        self.assertEqual('a', result[1])
        self.assertEqual(4, result[2])

    def test_repetitive(self):
        result = longest_seq.find('abababab')
        self.assertEqual(None,result)

class SearchFeynman:
    def __init__(self, n):
        self.n = n
    
    def pi_digits(n):
        "Generate n digits of Pi."
        k, a, b, a1, b1 = 2, 4, 1, 12, 4
        while n > 0:
            p, q, k = k * k, 2 * k + 1, k + 1
            a, b, a1, b1 = a1, b1, p * a + q * a1, p * b + q * b1
            d, d1 = a / b, a1 / b1
            while d == d1 and n > 0:
                yield int(d)
                n -= 1
                a, a1 = 10 * (a % b), 10 * (a1 % b1)
                d, d1 = a / b, a1 / b1

    def search(self):
        digits = [ k for k in map(str, SearchFeynman.pi_digits(self.n))]
        pi = digits[0] + '.' + ''.join(digits[1:])
        result = longest_seq.find(pi)
        if result is None:
            print('No sequence found')
        else:
            print('longest sequence of length %d is %s at %d' % (result[2], result[1]*result[2], result[0]))
            

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

    sf = SearchFeynman(100500)
    sf.search()