Simplify lookup of animation external commands.

anntzer · anntzer · commit 33bc9afceed7 · 2018-05-11T00:02:24.000-07:00
... by using shutil.which instead of trying to run the command.

Also, we don't need to explicitly call
ImageMagickBase._init_from_registry because the writers.register
decorator will do that for us (via the call to isAvailable).
diff --git a/lib/matplotlib/animation.py b/lib/matplotlib/animation.py
@@ -25,6 +25,7 @@
 import os
 from pathlib import Path
 import platform
+import shutil
 import subprocess
 import sys
 from tempfile import TemporaryDirectory
@@ -408,27 +409,9 @@ def bin_path(cls):
     @classmethod
     def isAvailable(cls):
         '''
-        Check to see if a MovieWriter subclass is actually available by
-        running the commandline tool.
+        Check to see if a MovieWriter subclass is actually available.
         '''
-        bin_path = cls.bin_path()
-        if not bin_path:
-            return False
-        try:
-            p = subprocess.Popen(
-                bin_path,
-                shell=False,
-                stdout=subprocess.PIPE,
-                stderr=subprocess.PIPE,
-                creationflags=subprocess_creation_flags)
-            return cls._handle_subprocess(p)
-        except OSError:
-            return False
-
-    @classmethod
-    def _handle_subprocess(cls, process):
-        process.communicate()
-        return True
+        return shutil.which(cls.bin_path()) is not None
 
 
 class FileMovieWriter(MovieWriter):
@@ -633,13 +616,14 @@ def output_args(self):
         return args + ['-y', self.outfile]
 
     @classmethod
-    def _handle_subprocess(cls, process):
-        _, err = process.communicate()
-        # Ubuntu 12.04 ships a broken ffmpeg binary which we shouldn't use
-        # NOTE : when removed, remove the same method in AVConvBase.
-        if 'Libav' in err.decode():
-            return False
-        return True
+    def isAvailable(cls):
+        return (
+            super().isAvailable()
+            # Ubuntu 12.04 ships a broken ffmpeg binary which we shouldn't use.
+            # NOTE: when removed, remove the same method in AVConvBase.
+            and b'LibAv' not in subprocess.run(
+                [cls.bin_path()], creationflags=subprocess_creation_flags,
+                stdout=subprocess.DEVNULL, stderr=subprocess.PIPE).stderr)
 
 
 # Combine FFMpeg options with pipe-based writing
@@ -697,9 +681,7 @@ class AVConvBase(FFMpegBase):
     args_key = 'animation.avconv_args'
 
     # NOTE : should be removed when the same method is removed in FFMpegBase.
-    @classmethod
-    def _handle_subprocess(cls, process):
-        return MovieWriter._handle_subprocess(process)
+    isAvailable = classmethod(MovieWriter.isAvailable.__func__)
 
 
 # Combine AVConv options with pipe-based writing
@@ -772,8 +754,6 @@ def isAvailable(cls):
             cls._init_from_registry()
         return super().isAvailable()
 
-ImageMagickBase._init_from_registry()
-
 
 # Note: the base classes need to be in that order to get
 # isAvailable() from ImageMagickBase called and not the
