Prevent exception when running animation on Agg backend.

anntzer · anntzer · commit 1b81a087db48 · 2019-01-19T20:06:43.000+01:00
Currently, running e.g. the strip_chart example using the agg backend
(not a particularly interesting use case, but done in particular by the
doc build) causes a "AttributeError: 'FuncAnimation' object has no
attribute '_cache_frame_data'" exception.

This is fixed by moving the setting of the `_cache_frame_data` attribute
to before the `super().__init__` call.

Also move the setting of `_init_func` next to the one of `_func`, which
seems to be a logical grouping.
diff --git a/lib/matplotlib/animation.py b/lib/matplotlib/animation.py
@@ -1613,6 +1613,7 @@ def __init__(self, fig, func, frames=None, init_func=None, fargs=None,
         else:
             self._args = ()
         self._func = func
+        self._init_func = init_func
 
         # Amount of framedata to keep around for saving movies. This is only
         # used if we don't know how many frames there will be: in the case
@@ -1644,7 +1645,7 @@ def __init__(self, fig, func, frames=None, init_func=None, fargs=None,
             # As a workaround, convert save_count to a native python int.
             self.save_count = int(self.save_count)
 
-        self._init_func = init_func
+        self._cache_frame_data = cache_frame_data
 
         # Needs to be initialized so the draw functions work without checking
         self._save_seq = []
@@ -1655,8 +1656,6 @@ def __init__(self, fig, func, frames=None, init_func=None, fargs=None,
         # for a single frame from init, which is not what we want.
         self._save_seq = []
 
-        self._cache_frame_data = cache_frame_data
-
     def new_frame_seq(self):
         # Use the generating function to generate a new frame sequence
         return self._iter_gen()
