On Fri, Sep 30, 2011 at 13:28, Nick Coghlan <ncoghlan@gmail.com> wrote:
On Fri, Sep 30, 2011 at 5:42 AM, Giampaolo Rodolà <g.rodola@gmail.com> wrote:
...or 2 in case you're not at the beginning of the file. before = f.tell() f.peeklines(10) f.seek(before)
A context manager to handle the tell()/seek() may be an interesting and more general purpose idea:
# In the io module class _TellSeek: def __init__(self, f): self._f = f def __enter__(self): self._position = self._f.tell() def __exit__(self, *args): self._f.seek(self._position)
def restore_position(f): return _TellSeek(f)
# Usage with io.restore_position(f): for i, line in enumerate(f, 1): # Do stuff if i == 10: break else: # Oops, didn't get as many lines as we wanted
This is useful, and made simpler by contextlib.contextmanager. Actually I just posted this snipped on G+ a couple of weeks ago, since I found it very useful for some stream-massaging code I was writing. And yes, it only makes sense for seekable streams, of course. So I'm -1 on the peeklines request, since it's easily implemented by other means. Eli