Problem

You’ve tried to add an object into a set and a TypeError: unhashable type: exception was raised. You were probably using a set because you needed a collection of objects without duplicates. If that was the case, two ways of solving this come to mind:

• Implement the __hash__ method for the parent class of that object as per the guidelines in the Python documentation.

• Extend the inbuilt data-type list and override it’s append() method:

  An instance of this class will behave exactly like a normal list, but won’t allow duplicates to be added to it.

  Note: The item object’s parent class needs to have it’s __eq__ method implemented for this to work.