update xy limits of a plot

def set_viewlimits(self, axes=None):
        """ update xy limits of a plot"""
        if axes is None:
            axes = self.axes

        xmin, xmax, ymin, ymax = self.data_range
        if len(self.conf.zoom_lims) >1:
            zlims = self.conf.zoom_lims[-1]
            if axes in zlims:
                xmin, xmax, ymin, ymax = zlims[axes]

        xmin = max(self.data_range[0], xmin)
        xmax = min(self.data_range[1], xmax)
        ymin = max(self.data_range[2], ymin)
        ymax = min(self.data_range[3], ymax)
        if (xmax < self.data_range[0] or
            xmin > self.data_range[1] or
            ymax < self.data_range[2] or
            ymin > self.data_range[3] ):
            self.conf.zoom_lims.pop()
            return

        if abs(xmax-xmin) < 2:
            xmin = int(0.5*(xmax+xmin) - 1)
            xmax = xmin + 2

        if abs(ymax-ymin) < 2:
            ymin = int(0.5*(ymax+xmin) - 1)
            ymax = ymin + 2

        self.axes.set_xlim((xmin, xmax),emit=True)
        self.axes.set_ylim((ymin, ymax),emit=True)
        self.axes.update_datalim(((xmin, ymin), (xmax, ymax)))

        self.conf.datalimits = [xmin, xmax, ymin, ymax]
        self.redraw()