added namespace module

git-svn-id: svn://svn.cy55.de/Zope3/src/cybertools/trunk@2487 fd906abe-77d9-0310-91a1-e0d9ade77398

util/namespace.py

@@ -0,0 +1,88 @@
+#
+#  Copyright (c) 2008 Helmut Merz helmutm@cy55.de
+#
+#  This program is free software; you can redistribute it and/or modify
+#  it under the terms of the GNU General Public License as published by
+#  the Free Software Foundation; either version 2 of the License, or
+#  (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program; if not, write to the Free Software
+#  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+#
+
+"""
+Special namespaces for execution of Python code, e.g. for implementing
+configuration or export/import formats, or providing a restricted Python
+for scripts or an interactive interpreter.
+
+$Id$
+"""
+
+import traceback
+
+_not_found = object()
+
+
+class BaseNamespace(dict):
+
+    builtins = 'dir', 'output'
+
+    def __init__(self, *args, **kw):
+        super(BaseNamespace, self).__init__(*args, **kw)
+        self['__builtins__'] = {}
+        for key in self.builtins:
+            self[key] = getattr(self, key)
+
+    def output(self, value):
+        print value
+
+    def dir(self, obj=None):
+        if obj is None:
+            return dir(self)
+        return dir(obj)
+
+    def __getitem__(self, key):
+        result = self.get(key, _not_found)
+        if result is _not_found:
+            raise NameError(key)
+        return result
+
+    def __getattr__(self, key):
+        result = self.get(key, _not_found)
+        if result is _not_found:
+            raise AttributeError(key)
+        return result
+
+
+class Symbol(object):
+
+    def __init__(self, namespace, name):
+        self.namespace = namespace
+        self.name = name
+
+    def __str__(self):
+        return self.name
+
+    def __repr__(self):
+        return "<Symbol '%s'>" % self.name
+
+
+class AutoNamespace(BaseNamespace):
+
+    symbolFactory = Symbol
+
+    def __getitem__(self, key):
+        result = self.get(key, _not_found)
+        if result is _not_found:
+            result = getattr(self, key, _not_found)
+            if result is _not_found:
+                sym = Symbol(self, key)
+                self[key] = sym
+                return sym
+        return result

util/namespace.txt

@@ -0,0 +1,63 @@
+==============================================
+Python Execution in Special Dynamic Namespaces
+==============================================
+
+$Id$
+
+  >>> from cybertools.util import namespace
+
+
+A Very Restricted Basic Namespace
+=================================
+
+  >>> minimal = namespace.BaseNamespace()
+
+We
+
+  >>> code = """
+  ... print 'Hello'
+  ... # a comment
+  ... print dir('')
+  ... print '__builtins__:', __builtins__
+  ... output('something')
+  ... a = 'a is a variable'
+  ... if a:
+  ...     print a
+  ... """
+  >>> exec code in minimal
+  Hello
+  ['__add__', ..., 'zfill']
+  __builtins__: {}
+  something
+  a is a variable
+
+Assignments in code executed in a namespace may be accessed as attributes
+of the namespace later.
+
+  >>> minimal.a
+  'a is a variable'
+
+By setting the ``__builtins__`` mapping to an empty dictionary the minimal
+namespace provides a secure restricted execution environment.
+
+  >>> exec "import os" in minimal
+  Traceback (most recent call last):
+  ...
+  ImportError: __import__ not found
+
+  >>> exec "f = open('dummy.txt', 'w')" in minimal
+  Traceback (most recent call last):
+  ...
+  NameError: open
+
+
+A Namespace Automatically Generating Symbols
+============================================
+
+  >>> auto = namespace.AutoNamespace()
+
+  >>> exec "print something" in auto
+  something
+
+  >>> auto.something
+  <Symbol 'something'>

util/tests.py

@@ -23,6 +23,7 @@ def test_suite():
         doctest.DocFileSuite('config.txt', optionflags=flags),
         doctest.DocFileSuite('defer.txt', optionflags=flags),
         doctest.DocFileSuite('format.txt', optionflags=flags),
+        doctest.DocFileSuite('namespace.txt', optionflags=flags),
         doctest.DocFileSuite('property.txt', optionflags=flags),
         doctest.DocFileSuite('jeep.txt', optionflags=flags),
         doctest.DocFileSuite('randomname.txt', optionflags=flags),