This is not possible out of the box because the matplotlib.widgets.Slider implementation uses axvspan and axvline to define the slider bar (which is patches.Polygon ) and updates it according to the horizontal assumption. It's not too difficult to write your own vertical slider using the horizontal slider as an example (you would also have to subclass from AxesWidget ), but you need to do this yourself.
Valid as of matplotlib 2.0: The following is a vertical slider class; it works the same as horizontal, except that ... well ... vertical!
from matplotlib.widgets import AxesWidget import six class VertSlider(AxesWidget): """ A slider representing a floating point range. For the slider to remain responsive you must maintain a reference to it. The following attributes are defined *ax* : the slider :class:`matplotlib.axes.Axes` instance *val* : the current slider value *hline* : a :class:`matplotlib.lines.Line2D` instance representing the initial value of the slider *poly* : A :class:`matplotlib.patches.Polygon` instance which is the slider knob *valfmt* : the format string for formatting the slider text *label* : a :class:`matplotlib.text.Text` instance for the slider label *closedmin* : whether the slider is closed on the minimum *closedmax* : whether the slider is closed on the maximum *slidermin* : another slider - if not *None*, this slider must be greater than *slidermin* *slidermax* : another slider - if not *None*, this slider must be less than *slidermax* *dragging* : allow for mouse dragging on slider Call :meth:`on_changed` to connect to the slider event """ def __init__(self, ax, label, valmin, valmax, valinit=0.5, valfmt='%1.2f', closedmin=True, closedmax=True, slidermin=None, slidermax=None, dragging=True, **kwargs): """ Create a slider from *valmin* to *valmax* in axes *ax*. Additional kwargs are passed on to ``self.poly`` which is the :class:`matplotlib.patches.Rectangle` which draws the slider knob. See the :class:`matplotlib.patches.Rectangle` documentation valid property names (eg, *facecolor*, *edgecolor*, *alpha*, ...). Parameters ---------- ax : Axes The Axes to put the slider in label : str Slider label valmin : float The minimum value of the slider valmax : float The maximum value of the slider valinit : float The slider initial position label : str The slider label valfmt : str Used to format the slider value, fprint format string closedmin : bool Indicate whether the slider interval is closed on the bottom closedmax : bool Indicate whether the slider interval is closed on the top slidermin : Slider or None Do not allow the current slider to have a value less than `slidermin` slidermax : Slider or None Do not allow the current slider to have a value greater than `slidermax` dragging : bool if the slider can be dragged by the mouse """ AxesWidget.__init__(self, ax) self.valmin = valmin self.valmax = valmax self.val = valinit self.valinit = valinit self.poly = ax.axhspan(valmin, valinit, 0, 1, **kwargs) self.hline = ax.axhline(valinit, 0, 1, color='r', lw=1) self.valfmt = valfmt ax.set_xticks([]) ax.set_ylim((valmin, valmax)) ax.set_yticks([]) ax.set_navigate(False) self.connect_event('button_press_event', self._update) self.connect_event('button_release_event', self._update) if dragging: self.connect_event('motion_notify_event', self._update) self.label = ax.text(0.5, 1.03, label, transform=ax.transAxes, verticalalignment='center', horizontalalignment='center') self.valtext = ax.text(0.5, -0.03, valfmt % valinit, transform=ax.transAxes, verticalalignment='center', horizontalalignment='center') self.cnt = 0 self.observers = {} self.closedmin = closedmin self.closedmax = closedmax self.slidermin = slidermin self.slidermax = slidermax self.drag_active = False def _update(self, event): """update the slider position""" if self.ignore(event): return if event.button != 1: return if event.name == 'button_press_event' and event.inaxes == self.ax: self.drag_active = True event.canvas.grab_mouse(self.ax) if not self.drag_active: return elif ((event.name == 'button_release_event') or (event.name == 'button_press_event' and event.inaxes != self.ax)): self.drag_active = False event.canvas.release_mouse(self.ax) return val = event.ydata if val <= self.valmin: if not self.closedmin: return val = self.valmin elif val >= self.valmax: if not self.closedmax: return val = self.valmax if self.slidermin is not None and val <= self.slidermin.val: if not self.closedmin: return val = self.slidermin.val if self.slidermax is not None and val >= self.slidermax.val: if not self.closedmax: return val = self.slidermax.val self.set_val(val) def set_val(self, val): xy = self.poly.xy xy[1] = 0, val xy[2] = 1, val self.poly.xy = xy self.valtext.set_text(self.valfmt % val) if self.drawon: self.ax.figure.canvas.draw_idle() self.val = val if not self.eventson: return for cid, func in six.iteritems(self.observers): func(val) def on_changed(self, func): """ When the slider value is changed, call *func* with the new slider position A connection id is returned which can be used to disconnect """ cid = self.cnt self.observers[cid] = func self.cnt += 1 return cid def disconnect(self, cid): """remove the observer with connection id *cid*""" try: del self.observers[cid] except KeyError: pass def reset(self): """reset the slider to the initial value if needed""" if (self.val != self.valinit): self.set_val(self.valinit)