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The one that emits the signal is an object, in your Helper it is not an object, but the name of a class, so the solution is to create an object. For another str and tuple are reserved words that indicate data types, in the case of pyqtSignal() its use is correct since pyqtSignal () requires as parameters the types of data it will handle, but do not use it as arguments in Emt() since you overlapped his name.

Whenever setModel() is called, a new selection model is created. Internally, the currentChanged signal of the new selection model is then connected to the protected currentChanged slot of the list-view. Thus, whenever a data model is set, the existing internal signal connections are automatically disconnected and reconnected. In your example, when you monkey-patch currentChanged after calling setModel(), the internal signal connections will not be re-made, and so your function will never be called.

In general, it is usually a mistake to make changes to a view before setting any of its models, because there are likely to be unpredictable internal side-effects which won't always be documented.

You should also note that it is not necessary to monkey-patch currentChanged at all. The correct way to do things is like this: