Matplotlib: drag’n’drop text example¶
Matplotlib provides event handling to determine things like key presses, mouse position, and button clicks. Matplotlib supports a number of GUIs, and provides an interface to the GUI event handling via the mpl_connect and mpl_disconnect methods.
This page gives an example of use of these facilities by adding a Drag'n'Drop handler for text objects. You can get the source code for this example here: Text_DragnDrop_v0.1.py .)
Defining the handler class¶
#!python numbers=disable from matplotlib import pylab as p from matplotlib.text import Text class DragHandler(object): """ A simple class to handle Drag n Drop. This is a simple example, which works for Text objects only """ def __init__(self, figure=None) : """ Create a new drag handler and connect it to the figure's event system. If the figure handler is not given, the current figure is used instead """ if figure is None : figure = p.gcf() # simple attibute to store the dragged text object self.dragged = None # Connect events and callbacks figure.canvas.mpl_connect("pick_event", self.on_pick_event) figure.canvas.mpl_connect("button_release_event", self.on_release_event) def on_pick_event(self, event): " Store which text object was picked and were the pick event occurs." if isinstance(event.artist, Text): self.dragged = event.artist self.pick_pos = (event.mouseevent.xdata, event.mouseevent.ydata) return True def on_release_event(self, event): " Update text position and redraw" if self.dragged is not None : old_pos = self.dragged.get_position() new_pos = (old_pos + event.xdata - self.pick_pos, old_pos + event.ydata - self.pick_pos) self.dragged.set_position(new_pos) self.dragged = None p.draw() return True
#! python numbers=disable # Usage example from numpy import * # Create arbitrary points and labels x, y = random.normal(5, 2, size=(2, 9)) labels = [ "Point %d" % i for i in xrange(x.size)] # trace a scatter plot p.scatter(x, y) p.grid() # add labels and set their picker attribute to True for a,b,l in zip(x,y, labels): p.text(a, b, l, picker=True) # Create the event hendler dragh = DragHandler() p.show()
The Text objects can now be moved with the mouse.
Section author: Elby