Defaut to writing animation frames to a temporary directory.

anntzer · anntzer · commit 5ee84280ed4a · 2020-01-03T16:28:30.000+01:00
(We could later deprecate clean_temp, as the user can simply pass a
non-None frame_prefix to write temporary frames whereever they want and
keep them there.)
diff --git a/doc/api/prev_api_changes/api_changes_3.2.0/behavior.rst b/doc/api/prev_api_changes/api_changes_3.2.0/behavior.rst
@@ -299,3 +299,9 @@ package, and Axes methods that take a ``norm`` parameter.
 
 If extra kwargs are passed to `.LogScale`, `TypeError` will now be
 raised instead of `ValueError`.
+
+`FileMovieWriter` temporary frames directory
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+`.FileMovieWriter` now defaults to writing temporary frames in a temporary
+directory, which is always cleared at exit.  In order to keep the individual
+frames saved on the filesystem, pass an explicit *frame_prefix*.
diff --git a/lib/matplotlib/animation.py b/lib/matplotlib/animation.py
@@ -431,7 +431,7 @@ def __init__(self, *args, **kwargs):
         MovieWriter.__init__(self, *args, **kwargs)
         self.frame_format = mpl.rcParams['animation.frame_format']
 
-    def setup(self, fig, outfile, dpi=None, frame_prefix='_tmp',
+    def setup(self, fig, outfile, dpi=None, frame_prefix=None,
               clear_temp=True):
         '''Perform setup for writing the movie file.
 
@@ -446,13 +446,13 @@ def setup(self, fig, outfile, dpi=None, frame_prefix='_tmp',
             controls the size in pixels of the resulting movie file.
             Default is fig.dpi.
         frame_prefix : str, optional
-            The filename prefix to use for temporary files.  Defaults to
-            ``'_tmp'``.
+            The filename prefix to use for temporary files.  If None (the
+            default), files are written to a temporary directory which is
+            deleted by `cleanup` (regardless of the value of *clear_temp*).
         clear_temp : bool, optional
             If the temporary files should be deleted after stitching
             the final result.  Setting this to ``False`` can be useful for
             debugging.  Defaults to ``True``.
-
         '''
         self.fig = fig
         self.outfile = outfile
@@ -461,8 +461,13 @@ def setup(self, fig, outfile, dpi=None, frame_prefix='_tmp',
         self.dpi = dpi
         self._adjust_frame_size()
 
+        if frame_prefix is None:
+            self._tmpdir = TemporaryDirectory()
+            self.temp_prefix = str(Path(self._tmpdir.name, 'tmp'))
+        else:
+            self._tmpdir = None
+            self.temp_prefix = frame_prefix
         self.clear_temp = clear_temp
-        self.temp_prefix = frame_prefix
         self._frame_counter = 0  # used for generating sequential file names
         self._temp_paths = list()
         self.fname_format_str = '%s%%07d.%s'
@@ -524,13 +529,15 @@ def finish(self):
 
     def cleanup(self):
         MovieWriter.cleanup(self)
-
-        # Delete temporary files
-        if self.clear_temp:
-            _log.debug('MovieWriter: clearing temporary paths=%s',
-                       self._temp_paths)
-            for path in self._temp_paths:
-                path.unlink()
+        if self._tmpdir:
+            _log.debug('MovieWriter: clearing temporary path=%s', self._tmpdir)
+            self._tmpdir.cleanup()
+        else:
+            if self.clear_temp:
+                _log.debug('MovieWriter: clearing temporary paths=%s',
+                           self._temp_paths)
+                for path in self._temp_paths:
+                    path.unlink()
 
 
 @writers.register('pillow')
