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MVP Model View Presenter

MVP splits your UI code into three roles:

1️⃣ Model — data & business logic - Holds application state - Knows nothing about Qt or UI - Example: data classes, domain logic, timers, IO, calculations

2️⃣ View — UI only - Widgets, layouts, rendering - Emits user intent (signals like clicked, textChanged) - Has no business logic - Does not pull data from Model

3️⃣ Presenter — the glue - Listens to View events - Updates the Model - Listens to Model changes - Pushes updates to the View

Simple Demo

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Model notify variant

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Brief remainder

Qt uses signals & slots to implement an event-driven, observer pattern.
pyqtSignal declares events; pyqtSlot receives them safely and efficiently.

  • Signal → “Something happened”
  • Slot → “What should run when it happens”

pyqtSignal

  • Declared at class level
  • Signal type is defined by argument list
  • Emits with .emit(...)
  • One signal → many receivers
declare
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from PyQt6.QtCore import QObject, pyqtSignal

class GreetingView(QWidget):
    # User intent exposed as signals
    nameChanged = pyqtSignal(str)

    def __init__(self) -> None:
        super().__init__()

        self.edit = QLineEdit()
        self.label = QLabel("Hello!")

        #...

        # UI → View signals
        self.edit.textChanged.connect(self.nameChanged.emit)

pyqtSlot

pyqtSlot marks a method as a Qt slot.

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from PyQt6.QtCore import pyqtSlot

class GreetingPresenter(QObject):
    @pyqtSlot(str)
    def on_name_changed(self, text: str) -> None:
        self.model.name = text
        self.view.set_greeting(self.model.greeting())

Reference