matplotlib · anntzer · Jan 14, 2020
diff --git a/examples/animation/animate_decay.py b/examples/animation/animate_decay.py
@@ -47,6 +47,6 @@ def run(data):
 
     return line,
 
-ani = animation.FuncAnimation(fig, run, data_gen, blit=False, interval=10,
-                              repeat=False, init_func=init)
+animation.FuncAnimation(fig, run, data_gen, blit=False, interval=10,
+                        repeat=False, init_func=init)
 plt.show()
diff --git a/examples/animation/animated_histogram.py b/examples/animation/animated_histogram.py
@@ -87,5 +87,5 @@ def animate(i):
 ax.set_xlim(left[0], right[-1])
 ax.set_ylim(bottom.min(), top.max())
 
-ani = animation.FuncAnimation(fig, animate, 100, repeat=False, blit=True)
+animation.FuncAnimation(fig, animate, 100, repeat=False, blit=True)
 plt.show()
diff --git a/examples/animation/bayes_update.py b/examples/animation/bayes_update.py
@@ -62,6 +62,6 @@ def __call__(self, i):
 
 fig, ax = plt.subplots()
 ud = UpdateDist(ax, prob=0.7)
-anim = FuncAnimation(fig, ud, frames=np.arange(100), init_func=ud.init,
-                     interval=100, blit=True)
+FuncAnimation(fig, ud, frames=np.arange(100), init_func=ud.init,
+              interval=100, blit=True)
 plt.show()
diff --git a/examples/animation/double_pendulum_sgskip.py b/examples/animation/double_pendulum_sgskip.py
@@ -94,6 +94,6 @@ def animate(i):
     return line, time_text
 
 
-ani = animation.FuncAnimation(fig, animate, range(1, len(y)),
-                              interval=dt*1000, blit=True, init_func=init)
+animation.FuncAnimation(fig, animate, range(1, len(y)),
+                        interval=dt*1000, blit=True, init_func=init)
 plt.show()
diff --git a/examples/animation/rain.py b/examples/animation/rain.py
@@ -67,5 +67,5 @@ def update(frame_number):
 
 
 # Construct the animation, using the update function as the animation director.
-animation = FuncAnimation(fig, update, interval=10)
+FuncAnimation(fig, update, interval=10)
 plt.show()
diff --git a/examples/animation/random_walk.py b/examples/animation/random_walk.py
@@ -68,7 +68,7 @@ def update_lines(num, data_lines, lines):
 ax.set_title('3D Test')
 
 # Creating the Animation object
-line_ani = animation.FuncAnimation(
+animation.FuncAnimation(
     fig, update_lines, 25, fargs=(data, lines), interval=50)
 
 plt.show()
diff --git a/examples/animation/strip_chart.py b/examples/animation/strip_chart.py
@@ -56,7 +56,6 @@ def emitter(p=0.03):
 scope = Scope(ax)
 
 # pass a generator in "emitter" to produce data for the update func
-ani = animation.FuncAnimation(fig, scope.update, emitter, interval=10,
-                              blit=True)
+animation.FuncAnimation(fig, scope.update, emitter, interval=10, blit=True)
 
 plt.show()
diff --git a/examples/animation/unchained.py b/examples/animation/unchained.py
@@ -69,5 +69,5 @@ def update(*args):
     return lines
 
 # Construct the animation, using the update function as the animation director.
-anim = animation.FuncAnimation(fig, update, interval=10)
+animation.FuncAnimation(fig, update, interval=10)
 plt.show()
diff --git a/lib/matplotlib/animation.py b/lib/matplotlib/animation.py
@@ -929,14 +929,17 @@ def __init__(self, fig, event_source=None, blit=False):
         self.frame_seq = self.new_frame_seq()
         self.event_source = event_source
 
+        # Wrapper lambdas prevent GC.
+
         # Instead of starting the event source now, we connect to the figure's
         # draw_event, so that we only start once the figure has been drawn.
-        self._first_draw_id = fig.canvas.mpl_connect('draw_event', self._start)
+        self._first_draw_id = fig.canvas.mpl_connect(
+            'draw_event', lambda event: self._start(event))
 
         # Connect to the figure's close_event so that we don't continue to
         # fire events and try to draw to a deleted figure.
-        self._close_id = self._fig.canvas.mpl_connect('close_event',
-                                                      self._stop)
+        self._close_id = self._fig.canvas.mpl_connect(
+            'close_event', lambda event: self._stop(event))
         if self._blit:
             self._setup_blit()
 

diff --git a/lib/matplotlib/widgets.py b/lib/matplotlib/widgets.py
@@ -94,14 +94,6 @@ class AxesWidget(Widget):
     """
     Widget connected to a single `~matplotlib.axes.Axes`.
 
-    To guarantee that the widget remains responsive and not garbage-collected,
-    a reference to the object should be maintained by the user.
-
-    This is necessary because the callback registry
-    maintains only weak-refs to the functions, which are member
-    functions of the widget.  If there are no references to the widget
-    object it may be garbage collected which will disconnect the callbacks.
-
     Attributes
     ----------
     ax : `~matplotlib.axes.Axes`
@@ -121,9 +113,11 @@ def connect_event(self, event, callback):
         Connect callback with an event.
 
         This should be used in lieu of `figure.canvas.mpl_connect` since this
-        function stores callback ids for later clean up.
+        function stores callback ids for later clean up, and sets up a wrapper
+        callback to prevent the original callback and thus the widget from
+        being garbage collected.
         """
-        cid = self.canvas.mpl_connect(event, callback)
+        cid = self.canvas.mpl_connect(event, lambda event: callback(event))
         self.cids.append(cid)
 
     def disconnect_events(self):
@@ -136,7 +130,6 @@ class Button(AxesWidget):
     """
     A GUI neutral button.
 
-    For the button to remain responsive you must keep a reference to it.
     Call `.on_clicked` to connect to the button.
 
     Attributes
@@ -247,9 +240,8 @@ class Slider(AxesWidget):
     """
     A slider representing a floating point range.
 
-    Create a slider from *valmin* to *valmax* in axes *ax*. For the slider to
-    remain responsive you must maintain a reference to it. Call
-    :meth:`on_changed` to connect to the slider event.
+    Create a slider from *valmin* to *valmax* in axes *ax*.
+    Call :meth:`on_changed` to connect to the slider event.
 
     Attributes
     ----------
@@ -505,9 +497,6 @@ class CheckButtons(AxesWidget):
     r"""
     A GUI neutral set of check buttons.
 
-    For the check buttons to remain responsive you must keep a
-    reference to this object.
-
     Connect to the CheckButtons with the `.on_clicked` method.
 
     Attributes
@@ -660,8 +649,6 @@ class TextBox(AxesWidget):
     """
     A GUI neutral text input box.
 
-    For the text box to remain responsive you must keep a reference to it.
-
     Call `.on_text_change` to be updated whenever the text changes.
 
     Call `.on_submit` to be updated whenever the user hits enter or
@@ -968,9 +955,6 @@ class RadioButtons(AxesWidget):
     """
     A GUI neutral radio button.
 
-    For the buttons to remain responsive you must keep a reference to this
-    object.
-
     Connect to the RadioButtons with the `.on_clicked` method.
 
     Attributes
@@ -1236,8 +1220,6 @@ class Cursor(AxesWidget):
     """
     A crosshair cursor that spans the axes and moves with mouse cursor.
 
-    For the cursor to remain responsive you must keep a reference to it.
-
     Parameters
     ----------
     ax : `matplotlib.axes.Axes`
@@ -1331,8 +1313,6 @@ class MultiCursor(Widget):
     Provide a vertical (default) and/or horizontal line cursor shared between
     multiple axes.
 
-    For the cursor to remain responsive you must keep a reference to it.
-
     Example usage::
 
         from matplotlib.widgets import MultiCursor
@@ -1386,9 +1366,11 @@ def __init__(self, canvas, axes, useblit=True, horizOn=False, vertOn=True,
 
     def connect(self):
         """connect events"""
-        self._cidmotion = self.canvas.mpl_connect('motion_notify_event',
-                                                  self.onmove)
-        self._ciddraw = self.canvas.mpl_connect('draw_event', self.clear)
+        # Wrapper lambdas prevent GC.
+        self._cidmotion = self.canvas.mpl_connect(
+            'motion_notify_event', lambda event: self.onmove(event))
+        self._ciddraw = self.canvas.mpl_connect(
+            'draw_event', lambda event: self.clear(event))
 
     def disconnect(self):
         """disconnect events"""
@@ -1656,8 +1638,6 @@ class SpanSelector(_SelectorWidget):
     Visually select a min/max range on a single axis and call a function with
     those values.
 
-    To guarantee that the selector remains responsive, keep a reference to it.
-
     In order to turn off the SpanSelector, set ``span_selector.active`` to
     False.  To turn it back on, set it to True.
 
@@ -1932,8 +1912,6 @@ class RectangleSelector(_SelectorWidget):
     """
     Select a rectangular region of an axes.
 
-    For the cursor to remain responsive you must keep a reference to it.
-
     Example usage::
 
         import numpy as np
@@ -2357,8 +2335,6 @@ class EllipseSelector(RectangleSelector):
     """
     Select an elliptical region of an axes.
 
-    For the cursor to remain responsive you must keep a reference to it.
-
     Example usage::
 
         import numpy as np
@@ -2427,8 +2403,6 @@ class LassoSelector(_SelectorWidget):
     """
     Selection curve of an arbitrary shape.
 
-    For the selector to remain responsive you must keep a reference to it.
-
     The selected path can be used in conjunction with `~.Path.contains_point`
     to select data points from an image.
 
@@ -2509,8 +2483,6 @@ class PolygonSelector(_SelectorWidget):
     drag anywhere in the axes to move all vertices. Press the *esc* key to
     start a new polygon.
 
-    For the selector to remain responsive you must keep a reference to it.
-
     Parameters
     ----------
     ax : `~matplotlib.axes.Axes`