1 files changed, 63 insertions, 0 deletions
diff --git a/module/SafeEval.py b/module/SafeEval.py
new file mode 100644
index 000000000..863ff48cc
--- /dev/null
+++ b/module/SafeEval.py
@@ -0,0 +1,63 @@
+## {{{ http://code.activestate.com/recipes/364469/ (r2)
+import compiler
+
+class Unsafe_Source_Error(Exception):
+    def __init__(self,error,descr = None,node = None):
+        self.error = error
+        self.descr = descr
+        self.node = node
+        self.lineno = getattr(node,"lineno",None)
+        
+    def __repr__(self):
+        return "Line %d.  %s: %s" % (self.lineno, self.error, self.descr)
+    __str__ = __repr__    
+           
+class SafeEval(object):
+    
+    def visit(self, node,**kw):
+        cls = node.__class__
+        meth = getattr(self,'visit'+cls.__name__,self.default)
+        return meth(node, **kw)
+            
+    def default(self, node, **kw):
+        for child in node.getChildNodes():
+            return self.visit(child, **kw)
+            
+    visitExpression = default
+    
+    def visitConst(self, node, **kw):
+        return node.value
+
+    def visitDict(self,node,**kw):
+        return dict([(self.visit(k),self.visit(v)) for k,v in node.items])
+        
+    def visitTuple(self,node, **kw):
+        return tuple(self.visit(i) for i in node.nodes)
+        
+    def visitList(self,node, **kw):
+        return [self.visit(i) for i in node.nodes]
+
+class SafeEvalWithErrors(SafeEval):
+
+    def default(self, node, **kw):
+        raise Unsafe_Source_Error("Unsupported source construct",
+                                node.__class__,node)
+            
+    def visitName(self,node, **kw):
+        raise Unsafe_Source_Error("Strings must be quoted", 
+                                 node.name, node)
+                                 
+    # Add more specific errors if desired
+            
+
+def safe_eval(source, fail_on_error = True):
+    walker = fail_on_error and SafeEvalWithErrors() or SafeEval()
+    try:
+        ast = compiler.parse(source,"eval")
+    except SyntaxError, err:
+        raise
+    try:
+        return walker.visit(ast)
+    except Unsafe_Source_Error, err:
+        raise
+## end of http://code.activestate.com/recipes/364469/ }}}