how do I "peek" into the next line?

[les_ander at yahoo.com]

OK, I am sorry , I did not explain my problem completely.
I can easily break from the loop when I see the character in a line
that I just read; however my problem involves putting back the line I
just read since if I have seen this special character, I have read one
line too many. Let me illustrate
suppose the file has 3 lines

line1.line1.line1
>line2.line2.line
line3.line3.line3

now suppose I have read the first line already.
then I read the second line and notice
that there is a ">" in front (my special character)
then I want the put back the second line into the
file or the stdin.

An easy way is if i read all the lines in to an array
and then I can put back the line with the special
character back into this array. However,
this file I am readding is huge! and I can read
it all in one swoop (not enough memory).

for x in stdin:
if x[0]==">":
#### put back the x some how... <-----
break
  else:
      print x

I hope this is clear
thanks