如何从连接到pyqt5 UI按钮对象的函数返回字符串

Question

我是QT的新手，我很难使用返回视频路径字符串的函数。此功能由Qt设计器生成的GUI按钮连接。当我尝试时，变量显示

<PyQt5.QtCore.QMetaObject.Connection object at 0x00000190D9F017B8>

这是我的代码。

import definition as df
from PyQt5 import uic, QtCore, QtGui, QtWidgets
import tkinter as tk
from tkinter import filedialog
import resources

root = tk.Tk()
root.withdraw()


def add_video():
    source_video = filedialog.askopenfilename(title="Select file",
                                          filetypes=(("MP4 File", 
                                      "*.mp4"), ("All Files", "*.*")))
    dlg.txt_inputPath.setText(source_video)
    dlg.txt_outputPath.setText(source_video[:-3]+"avi")

    return source_video


def output():
    outfile = filedialog.asksaveasfilename(title="file Name",
                                       filetypes=("AVI File", "*.avi"))
    dlg.txt_outputPath.setText(outfile)


def save_next():
    print("here")
    dlg.stackedWidget.setCurrentIndex(1)
    extracted_audio = df.extract_audio(video)
    text = df.audio_to_text(extracted_audio)
    word_token = df.tokenize(text)
    df.merge_video(video, word_token)


app = QtWidgets.QApplication([])
dlg = uic.loadUi("UI/mainwindow.ui")
video = dlg.btn_addvideo.clicked.connect(add_video)

dlg.btn_output.clicked.connect(output)
print(video)

dlg.btn_next.clicked.connect(save_next)


dlg.show()
app.exec()