electrum-bitcoinprivate/gui/kivy/uix/ui_screens/password.kv

Popup:
    id: popup
    title: _('Enter PIN Code')

    BoxLayout:

        orientation: 'vertical'

        Label:
            id: a
            text: '*'*len(kb.password)
            size_hint: 1, None
            height: '48dp'

        GridLayout:
            id: kb
            update_text: app.update_password
            password: ''
            on_password: if len(self.password) == 6: popup.dismiss()
            size_hint: 1, None
            height: '300dp'
            cols: 3
            KButton:
                text: '1'
            KButton:
                text: '2'
            KButton:
                text: '3'
            KButton:
                text: '4'
            KButton:
                text: '5'
            KButton:
                text: '6'
            KButton:
                text: '7'
            KButton:
                text: '8'
            KButton:
                text: '9'
            KButton:
                text: 'Clear'
            KButton:
                text: '0'
            KButton:
                text: '<'

        Widget:
            size_hint: 1, 1