remove unused '_save_seq' data attribute in 'FuncAnimation' class. fixes #8528.

pclove1 · pclove1 · commit 6254645bddfc · 2018-08-19T22:12:16.000-07:00
diff --git a/lib/matplotlib/animation.py b/lib/matplotlib/animation.py
@@ -1661,49 +1661,34 @@ def __init__(self, fig, func, frames=None, init_func=None, fargs=None,
 
         self._init_func = init_func
 
-        # Needs to be initialized so the draw functions work without checking
-        self._save_seq = []
-
         TimedAnimation.__init__(self, fig, **kwargs)
 
-        # Need to reset the saved seq, since right now it will contain data
-        # for a single frame from init, which is not what we want.
-        self._save_seq = []
-
     def new_frame_seq(self):
         # Use the generating function to generate a new frame sequence
         return self._iter_gen()
 
     def new_saved_frame_seq(self):
-        # Generate an iterator for the sequence of saved data. If there are
-        # no saved frames, generate a new frame sequence and take the first
-        # save_count entries in it.
-        if self._save_seq:
-            # While iterating we are going to update _save_seq
-            # so make a copy to safely iterate over
-            self._old_saved_seq = list(self._save_seq)
-            return iter(self._old_saved_seq)
+        # Generate a new frame sequence
+        # and take the first save_count entries in it.
+        if self.save_count is not None:
+            return itertools.islice(self.new_frame_seq(), self.save_count)
         else:
-            if self.save_count is not None:
-                return itertools.islice(self.new_frame_seq(), self.save_count)
+            frame_seq = self.new_frame_seq()
 
-            else:
-                frame_seq = self.new_frame_seq()
-
-                def gen():
-                    try:
-                        for _ in range(100):
-                            yield next(frame_seq)
-                    except StopIteration:
-                        pass
-                    else:
-                        cbook.warn_deprecated(
-                            "2.2", "FuncAnimation.save has truncated your "
-                            "animation to 100 frames.  In the future, no such "
-                            "truncation will occur; please pass 'save_count' "
-                            "accordingly.")
-
-                return gen()
+            def gen():
+                try:
+                    for _ in range(100):
+                        yield next(frame_seq)
+                except StopIteration:
+                    pass
+                else:
+                    cbook.warn_deprecated(
+                        "2.2", "FuncAnimation.save has truncated your "
+                        "animation to 100 frames.  In the future, no such "
+                        "truncation will occur; please pass 'save_count' "
+                        "accordingly.")
+
+            return gen()
 
     def _init_draw(self):
         # Initialize the drawing either using the given init_func or by
@@ -1721,16 +1706,8 @@ def _init_draw(self):
                                        'sequence of Artist objects.')
                 for a in self._drawn_artists:
                     a.set_animated(self._blit)
-        self._save_seq = []
 
     def _draw_frame(self, framedata):
-        # Save the data for potential saving of movies.
-        self._save_seq.append(framedata)
-
-        # Make sure to respect save_count (keep only the last save_count
-        # around)
-        self._save_seq = self._save_seq[-self.save_count:]
-
         # Call the func with framedata and args. If blitting is desired,
         # func needs to return a sequence of any artists that were modified.
         self._drawn_artists = self._func(framedata, *self._args)
diff --git a/lib/matplotlib/tests/test_animation.py b/lib/matplotlib/tests/test_animation.py
@@ -1,6 +1,7 @@
 import os
 from pathlib import Path
 import sys
+import weakref
 
 import numpy as np
 import pytest
@@ -260,3 +261,44 @@ def test_failing_ffmpeg(tmpdir, monkeypatch):
                 make_animation().save("test.mpeg")
     finally:
         animation.writers.reset_available_writers()
+
+
+def test_funcanimation_does_not_hold_references_to_frames():
+    fig, ax = plt.subplots()
+    line, = ax.plot([], [])
+
+    class Frame(dict):
+        # this subclassing enables to use weakref.ref()
+        pass
+
+    def init():
+        line.set_data([], [])
+        return line,
+
+    def animate(frame):
+        line.set_data(frame['x'], frame['y'])
+        return line,
+
+    frames_generated = []
+
+    def frames_generator():
+        for _ in range(5):
+            x = np.linspace(0, 10, 100)
+            y = np.random.rand(100)
+
+            frame = Frame(x=x, y=y)
+
+            # collect weak references to frames
+            # to validate their references later
+            frames_generated.append(weakref.ref(frame))
+
+            yield frame
+
+    anim = animation.FuncAnimation(fig, animate, init_func=init,
+                                   frames=frames_generator, save_count=5)
+
+    writer = NullMovieWriter()
+    anim.save('unused.null', writer=writer)
+
+    for f in frames_generated:
+        assert f() is None
