Immediate Circular Routes

pi = ''

with open('/path/to/pi_20m.txt') as the_file: pi = the_file.read()

for i in range(1, 1000000):
    s = str(i)

    end_of = pi.find(s) + len(s)
    end_of2 = pi.find(str(end_of)) + len(str(end_of))

    if end_of2 == i and end_of != i:
        print('\n' + str(i) + ' first appears in Pi at the end of ' + str(end_of) + ' digits')
        print(str(end_of) + ' first appears in Pi at the end of ' + str(end_of2) + ' digits\n')

    if i % 10000 == 0:
        print('At number ' + str(i))