Add single-use anonymous namespaces

README.md

@@ -51,6 +51,9 @@ execution equivalent to not using such keyword.
 Mutable objects in the user namespace can be altered (e.g. appending an item
 to a list).
 
+If `<space-name>` is blank, the cell is executed in a single-use anonymous
+namespace, which cannot be accessed later.
+
 ### Remove a space
 
 ```python

src/jupyter_spaces/__init__.py

@@ -1,5 +1,5 @@
 """Jupyter Spaces is an IPython extension for creating parallel namespaces
-availabe within the user namespace. It is designed to be used via IPython
+available within the user namespace. It is designed to be used via IPython
 magics in Jupyter notebooks.
 
 Copyright (c) 2018 Davide Sarra.

src/jupyter_spaces/magics.py

@@ -16,6 +16,8 @@ def space(self, line, cell):
             line (str): Content following `%%space` magic call, expected to
                 match the space name. If the provided space name has already
                 been used and not been removed, the same space object is used.
+                Unless the name is blank, in which case a unique anonymous
+                namespace is used.
             cell (str): Content following the first line.
 
         Examples:

src/jupyter_spaces/space.py

@@ -23,7 +23,7 @@ def register(self):
 
     def get_space(self, name, outer_space):
         """Get existing Space if a Space has the same name, otherwise create
-        and get new Space.
+        and get new Space. Blank name creates a single-use anonymous Space.
 
         Args:
             name (str): Name of the Space.
@@ -32,9 +32,13 @@ def get_space(self, name, outer_space):
         Returns:
             Space: Space.
         """
-        if name not in self._register:
-            self._register[name] = Space(name=name, outer_space=outer_space)
-        return self._register[name]
+        space = self._register.get(name)
+        if space is not None:
+            return space
+        space = Space(name=name, outer_space=outer_space)
+        if name:
+            self._register[name] = space
+        return space
 
     def remove_space(self, name):
         """Remove Space from register.

tests/test_magics.py

@@ -178,3 +178,8 @@ def test_none_does_not_produce_any_stdout(ip, capsys):
 def test_statement_does_not_produce_any_stdout(ip, capsys):
     ip.run_cell_magic(magic_name="space", line="tomato", cell="x = 1")
     assert capsys.readouterr().out == ""
+
+
+def test_anonymous_spaces(ip, capsys):
+    ip.run_cell_magic(magic_name="space", line="", cell="x = 1")
+    ip.run_cell_magic(magic_name="space", line="", cell="assert 'x' not in globals()")

tests/test_space.py

@@ -134,6 +134,12 @@ def test_get_existing_space(self):
         space2 = space_register.get_space(name="tomato", outer_space={})
         assert space1 is space2
 
+    def test_get_anonymous_space(self):
+        space_register = SpaceRegister()
+        space1 = space_register.get_space(name="", outer_space={})
+        space2 = space_register.get_space(name="", outer_space={})
+        assert space1 is not space2
+
     def test_remove_existing_space(self):
         space_register = SpaceRegister()
         space_register.get_space(name="tomato", outer_space={})