Object key existence check not consistent with lua

[sronsiek]

I have a Lua function that receives a python dict-based object 'attributes' (from sqlachemy) as argument and want to check for presence of a key - as per python hasattr(obj, 'some_key').

In Lua I would use:

if attribues['somekey'] ~= nil then
  -- key exists ...

but lupa raises a KeyError or AttibuteError exceptions - also using python.as_itemgetter or pyhton.as_attrgetter.

This forces me to use pcall to handle the exception:

if pcall( function( attr, key ) return attr[key] end, attributes, 'cost') then
   print( "cost found")
else
   print( "cost not found")
end

Is there a more convenient method for lupa to test key existence? It feels like there should be - perhaps I missed something. Reason for the qu is that the lua code is exposed to and editable by end users of an app - which will be a cause for confusion.

[kubber]

Did you manage to find a workaround? I'm having the same problem.

[sronsiek]

As per the original post, the starting point is a python object. My solution was to implement has_attr in the object's python model:

Case sensitive:

    def has_attr(self, attr):
        return attr in self.attributes

Case insensitive:

    def has_attr(self, attr):
        lattr = attr.lower()
        for key in self.attributes:
           if key.lower() == lattr:
               return True
        return False

with that in place I can now call has_attr on the object from Lua:

    if myObj.has_attr('some_key') then
        - key exists ...