identical.py

from marrow.schema import Attribute
from marrow.schema.validate import Validator
from marrow.schama.validate.exc import Concern

class EqualsOther(Validator):
	"""Ensure the value used matches an existing value from another attribute on the same object."""
  
	other = Attribute()
	
	def validate(self, value, context):
		other = getattr(context, self.other, None)
		
		if value != other:
			raise Concern("Values do not match.")
		
		return value