### Continued fraction expansion of quadratic irrationals

Let me emphasize that **I am very new to sage** and to computing in general, but I did research as much as I ~~can ~~could before asking this question.

It is well know that that quadratic irrationals has **eventually** periodic continued fraction expansion. I really tried to find a function that gives me the period of a given quadratic irrational. The best I could find was in this forum:
http://www.mail-archive.com/sage-support@googlegroups.com/msg04201.html

It explains that you can get using GAP the PrePeriod+Period. It has two disadvantages: the first, you can't get the pure period, i.e., without the preperiod, and the second is that it is ~~defined using ~~the input is not the number itself but the polynomial ~~and only the ones with one ~~it solve. If this polynomial has many positive ~~root works.~~roots it is a problem...

I tried to look also in PARI and didn't find anything.
I did see that it is written that sage itself does not have this function.

Let me also remark that such algorithm exist.
My question: Is there a way (via packages that are contained in sage) to find the period of a given quadratic irrational?

Thanks a lot!
Menny