intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 74 insertions, 0 deletions

diff --git a/contrib/python/ipython/py3/IPython/utils/contexts.py b/contrib/python/ipython/py3/IPython/utils/contexts.py
new file mode 100644
index 0000000000..4d379b0eda
--- /dev/null
+++ b/contrib/python/ipython/py3/IPython/utils/contexts.py
@@ -0,0 +1,74 @@
+# encoding: utf-8
+"""Miscellaneous context managers.
+"""
+
+import warnings
+
+# Copyright (c) IPython Development Team.
+# Distributed under the terms of the Modified BSD License.
+
+class preserve_keys(object):
+    """Preserve a set of keys in a dictionary.
+
+    Upon entering the context manager the current values of the keys
+    will be saved. Upon exiting, the dictionary will be updated to
+    restore the original value of the preserved keys. Preserved keys
+    which did not exist when entering the context manager will be
+    deleted.
+
+    Examples
+    --------
+
+    >>> d = {'a': 1, 'b': 2, 'c': 3}
+    >>> with preserve_keys(d, 'b', 'c', 'd'):
+    ...     del d['a']
+    ...     del d['b']      # will be reset to 2
+    ...     d['c'] = None   # will be reset to 3
+    ...     d['d'] = 4      # will be deleted
+    ...     d['e'] = 5
+    ...     print(sorted(d.items()))
+    ...
+    [('c', None), ('d', 4), ('e', 5)]
+    >>> print(sorted(d.items()))
+    [('b', 2), ('c', 3), ('e', 5)]
+    """
+
+    def __init__(self, dictionary, *keys):
+        self.dictionary = dictionary
+        self.keys = keys
+
+    def __enter__(self):
+        # Actions to perform upon exiting.
+        to_delete = []
+        to_update = {}
+
+        d = self.dictionary
+        for k in self.keys:
+            if k in d:
+                to_update[k] = d[k]
+            else:
+                to_delete.append(k)
+
+        self.to_delete = to_delete
+        self.to_update = to_update
+
+    def __exit__(self, *exc_info):
+        d = self.dictionary
+
+        for k in self.to_delete:
+            d.pop(k, None)
+        d.update(self.to_update)
+
+
+class NoOpContext(object):
+    """
+    Deprecated
+    
+    Context manager that does nothing."""
+
+    def __init__(self):
+        warnings.warn("""NoOpContext is deprecated since IPython 5.0 """,
+                                            DeprecationWarning, stacklevel=2)
+
+    def __enter__(self): pass
+    def __exit__(self, type, value, traceback): pass