How to unget a line when reading from a file/stream iterator/generator?

[python at bdurham.com]

Is there an elegant way to unget a line when reading from a file/stream
iterator/generator?

By "unget" I mean a way to push back a line into the source stream and
backtrack the iterator/generator one step?

The only alternative I can see is to put my line reading in a while-True
loop (vs. a for-loop) that manually calls my file/stream
iterator/generator's .next() method while manually handling the
StopIteration exception. Doesn't sound too elegant.

Is there a Pythonic design pattern/best practice that I can apply here?

Thank you,
Malcolm