Class LenientLookup

object --+    
         |    
LookupBase --+
             |
            LenientLookup

Default variable lookup mechanism for expressions.

When an undefined variable is referenced using this lookup style, the reference evaluates to an instance of the Undefined class:

>>> expr = Expression('nothing', lookup='lenient')
>>> undef = expr.evaluate({})
>>> undef
<Undefined 'nothing'>

The same will happen when a non-existing attribute or item is accessed on an existing object:

>>> expr = Expression('something.nil', lookup='lenient')
>>> expr.evaluate({'something': dict()})
<Undefined 'nil'>

See the documentation of the Undefined class for details on the behavior of such objects.