¿Es posible pasar variables a través de las ranuras para que pueda imprimir cierto texto? Intentando pasar la variable 'DiffP' que se define en otra función al slot.

'DiffP' cambia según el archivo seleccionado.

def addLineEdit(self):
    try:
        self.clearLayout()
        self.FileButton ={}
        self.Input = {}
        self.TotalInput = []
        for i in range(int(self.numberLine.text())):
            self.FileButton[i] = QtWidgets.QPushButton(self.centralwidget)
            self.FileButton[i].setText('Case {}'.format(i+1))
            self.FileButton[i].setFlat(True)
            self.FileButton[i].setMaximumSize(QtCore.QSize(50, 50))
            self.hboxlayout[0].addWidget(self.FileButton[i])
            self.FileButton[i].clicked.connect(lambda i=i: self.openfile(i))
            self.buttonGroup.addButton(self.FileButton[i],i)
            self.buttonGroup.buttonClicked['int'].connect(self.input)

def searchfile(self,dir):
        with open(dir) as f:
            content = f.readlines()
            MainList = content[44].split()
            RPM = round(float(MainList[0]), 2)
            Ps = round(float(MainList[1]), 2)
            Ts = round(float(MainList[2]), 2)
            Pd = round(float(MainList[3]), 2)
            Ratio = round(Pd / Ps, 2)
            DiffP = round(Pd - Ps, 2)
@pyqtSlot(int)
def input(self,button_or_id,DiffP):
    if isinstance(button_or_id, int):
        if button_or_id == 0:
            self.TotalInput[0].setText(str(DiffP))
        elif button_or_id == 1:
            self.TotalInput[54].setText('1')

def openfile(self,i):
    filename = QtWidgets.QFileDialog.getOpenFileName(self, 'Choose file')
    dir = filename[0]
    directory = os.path.split(dir)[0]
    return self.searchfile(dir)