#! usr/bin/python

import shelve


quotes = ['insert your quotes here', 'they should use single quotes', 'there is a comma separating them']


database = shelve.open('/path/to/quotes.dat')
try:
    database['index']
except:
    database['index'] = 0
finally:
    index = database['index']
    database['index'] = (index + 1) % len(quotes)
database.close()

print quotes[index]