Backwards compatibility hack to use nested() in Python 3.2

IPython/utils/nested_context.py

@@ -0,0 +1,50
+"""Backwards compatibility - we use contextlib.nested to support Python 2.6,
+but it's removed in Python 3.2."""
+
+# TODO : Remove this once we drop support for Python 2.6, and use
+# "with a, b:" instead.
+
+from contextlib import contextmanager
+
+@contextmanager
+def nested(*managers):
+    """Combine multiple context managers into a single nested context manager.
+
+   This function has been deprecated in favour of the multiple manager form
+   of the with statement.
+
+   The one advantage of this function over the multiple manager form of the
+   with statement is that argument unpacking allows it to be
+   used with a variable number of context managers as follows:
+
+      with nested(*managers):
+          do_something()
+
+    """
+    warn("With-statements now directly support multiple context managers",
+         DeprecationWarning, 3)
+    exits = []
+    vars = []
+    exc = (None, None, None)
+    try:
+        for mgr in managers:
+            exit = mgr.__exit__
+            enter = mgr.__enter__
+            vars.append(enter())
+            exits.append(exit)
+        yield vars
+    except:
+        exc = sys.exc_info()
+    finally:
+        while exits:
+            exit = exits.pop()
+            try:
+                if exit(*exc):
+                    exc = (None, None, None)
+            except:
+                exc = sys.exc_info()
+        if exc != (None, None, None):
+            # Don't rely on sys.exc_info() still containing
+            # the right information. Another exception may
+            # have been raised and caught by an exit method
+            raise exc[0], exc[1], exc[2]

IPython/core/interactiveshell.py

@@ -29,7 +29,10 import re
 import sys
 import tempfile
 import types
-from contextlib import nested
+try:
+    from contextlib import nested
+except:
+    from IPython.utils.nested_context import nested
 
 from IPython.config.configurable import SingletonConfigurable
 from IPython.core import debugger, oinspect

IPython/frontend/terminal/embed.py

@@ -26,7 +26,10 from __future__ import with_statement
 import __main__
 
 import sys
-from contextlib import nested
+try:
+    from contextlib import nested
+except:
+    from IPython.utils.nested_context import nested
 
 from IPython.core import ultratb
 from IPython.frontend.terminal.interactiveshell import TerminalInteractiveShell

IPython/frontend/terminal/interactiveshell.py

@@ -16,11 +16,15
 
 import __builtin__
 import bdb
-from contextlib import nested
 import os
 import re
 import sys
 
+try:
+    from contextlib import nested
+except:
+    from IPython.utils.nested_context import nested
+
 from IPython.core.error import TryNext
 from IPython.core.usage import interactive_usage, default_banner
 from IPython.core.interactiveshell import InteractiveShell, InteractiveShellABC