code: def GetFilePathsWithDialog(fileTypes=[]):
      
      root = tkinter.Tk()
      root.withdraw()
      filepath = filedialog.askopenfilenames(
          filetypes=fileTypes, parent=root)
  
      if isinstance(filepath, str):
          fileList = filepath.split(" ")
      elif isinstance(filepath, tuple):
          fileList = list(filepath)
      elif isinstance(filepath, list):
          fileList = filepath
  
      root.destroy()
      print(str(len(fileList)) + " files are selected")
  
      return fileList
docs: Multipul File Select with dialog
  
          fileTypes: you can choise file extension
              ex) fileTypes=[('Excel Files', '.xlsx')]