Fixes matplotlib#1862: The PS backend would inadvertently close file handles passed to it on Python 3. The TextIOWrapper that handles the encoding from unicode to ascii needs to be detached before its destructor is called, otherwise it will call close on the underlying file object. Also cleans up how with statements are handled to avoid the sometimes problematic null contextmanager.

Author: mdboom

lib/matplotlib/backends/backend_ps.py

@@ -5,7 +5,6 @@
 # PY3KTODO: Get rid of "print >>fh" syntax
 
 from __future__ import division, print_function
-import contextlib
 import glob, math, os, shutil, sys, time
 def _fn_name(): return sys._getframe(1).f_code.co_name
 import io
@@ -974,11 +973,6 @@ def print_ps(self, outfile, *args, **kwargs):
     def print_eps(self, outfile, *args, **kwargs):
         return self._print_ps(outfile, 'eps', *args, **kwargs)
 
-
-
-
-
-
     def _print_ps(self, outfile, format, *args, **kwargs):
         papertype = kwargs.pop("papertype", rcParams['ps.papersize'])
         papertype = papertype.lower()
@@ -1106,21 +1100,7 @@ def write(self, *kl, **kwargs):
         self.figure.set_facecolor(origfacecolor)
         self.figure.set_edgecolor(origedgecolor)
 
-        if rcParams['ps.usedistiller']:
-            # We are going to use an external program to process the output.
-            # Write to a temporary file.
-            fd, tmpfile = mkstemp()
-            context_manager = io.open(fd, 'wb')
-        else:
-            # Write directly to outfile.
-            if passed_in_file_object:
-                @contextlib.contextmanager
-                def null_context(value):
-                    yield value
-                context_manager = null_context(outfile)
-            else:
-                context_manager = open(outfile, 'wb')
-        with context_manager as raw_fh:
+        def print_figure_impl():
             if sys.version_info[0] >= 3:
                 fh = io.TextIOWrapper(raw_fh, encoding="ascii")
             else:
@@ -1195,6 +1175,24 @@ def null_context(value):
             if not isEPSF: print("%%EOF", file=fh)
             fh.flush()
 
+            if sys.version_info[0] >= 3:
+                fh.detach()
+
+        if rcParams['ps.usedistiller']:
+            # We are going to use an external program to process the output.
+            # Write to a temporary file.
+            fd, tmpfile = mkstemp()
+            with io.open(fd, 'wb') as raw_fh:
+                print_figure_impl()
+        else:
+            # Write directly to outfile.
+            if passed_in_file_object:
+                raw_fh = outfile
+                print_figure_impl()
+            else:
+                with open(outfile, 'wb') as raw_fh:
+                    print_figure_impl()
+
         if rcParams['ps.usedistiller']:
             if rcParams['ps.usedistiller'] == 'ghostscript':
                 gs_distill(tmpfile, isEPSF, ptype=papertype, bbox=bbox)