Late Edit / Shameless Plug: this is now available (with much more functionality) mpldatacursor . Calling mpldatacursor.datacursor() will allow it to be used by all matplotlib artists (including basic support for z-values in images, etc.).
As far as I know, not a single one has already been implemented, but it's not too difficult to write something like this:
import matplotlib.pyplot as plt class DataCursor(object): text_template = 'x: %0.2f\ny: %0.2f' x, y = 0.0, 0.0 xoffset, yoffset = -20, 20 text_template = 'x: %0.2f\ny: %0.2f' def __init__(self, ax): self.ax = ax self.annotation = ax.annotate(self.text_template, xy=(self.x, self.y), xytext=(self.xoffset, self.yoffset), textcoords='offset points', ha='right', va='bottom', bbox=dict(boxstyle='round,pad=0.5', fc='yellow', alpha=0.5), arrowprops=dict(arrowstyle='->', connectionstyle='arc3,rad=0') ) self.annotation.set_visible(False) def __call__(self, event): self.event = event
At least a few people seem to be using this, I have added an updated version below.
The new version has easier use and much more documentation (like a tiny bit).
Basically you would use it like this:
plt.figure() plt.subplot(2,1,1) line1, = plt.plot(range(10), 'ro-') plt.subplot(2,1,2) line2, = plt.plot(range(10), 'bo-') DataCursor([line1, line2]) plt.show()
The main differences are that a) there is no need to manually call line.set_picker(...) , b) there is no need to manually call fig.canvas.mpl_connect , and c) this version processes several axes and several digits.
from matplotlib import cbook class DataCursor(object): """A simple data cursor widget that displays the x,y location of a matplotlib artist when it is selected.""" def __init__(self, artists, tolerance=5, offsets=(-20, 20), template='x: %0.2f\ny: %0.2f', display_all=False): """Create the data cursor and connect it to the relevant figure. "artists" is the matplotlib artist or sequence of artists that will be selected. "tolerance" is the radius (in points) that the mouse click must be within to select the artist. "offsets" is a tuple of (x,y) offsets in points from the selected point to the displayed annotation box "template" is the format string to be used. Note: For compatibility with older versions of python, this uses the old-style (%) formatting specification. "display_all" controls whether more than one annotation box will be shown if there are multiple axes. Only one will be shown per-axis, regardless. """ self.template = template self.offsets = offsets self.display_all = display_all if not cbook.iterable(artists): artists = [artists] self.artists = artists self.axes = tuple(set(art.axes for art in self.artists)) self.figures = tuple(set(ax.figure for ax in self.axes)) self.annotations = {} for ax in self.axes: self.annotations[ax] = self.annotate(ax) for artist in self.artists: artist.set_picker(tolerance) for fig in self.figures: fig.canvas.mpl_connect('pick_event', self) def annotate(self, ax): """Draws and hides the annotation box for the given axis "ax".""" annotation = ax.annotate(self.template, xy=(0, 0), ha='right', xytext=self.offsets, textcoords='offset points', va='bottom', bbox=dict(boxstyle='round,pad=0.5', fc='yellow', alpha=0.5), arrowprops=dict(arrowstyle='->', connectionstyle='arc3,rad=0') ) annotation.set_visible(False) return annotation def __call__(self, event): """Intended to be called through "mpl_connect"."""