In Louisville, Kentucky, a female Python laid eggs two years ago. Among those, six were successfully incubated. Zookeepers initially thought that the female had had an encounter with a male python before she was taken in captivity. Since then, genetic analyses of the shedding skins of the mother and her offspring have revealed that she is the only parent to those babies. A phenomenon called parthenogenesis, which is quite rare, particularly with those big snakes.
Source : http://www.washingtonpost.com