Is it possible to have autoscale for the yaxis use only the current xlim rather than the whole series that was plotted?

For example, if I have a 2 year time-series with current xlim set to only show a 1 year span, how can I get matplotlib to base the autoscale for the y-axis on the 1 year span and not the full 2 year span?

For a dynamic plot where the user can shift the xlims it would be very nice to do this directly in matplotlib rather than having to use logic/data outside of matplotlib.