[Tkinter] MultiThreading Return value issue

[AvisPaul1]

Hi,

I have a small GUI program which reads a drives content and saves it in a csv file. The scanning of the drive takes some time and I am trying to put it into a separate thread. I wrote the following code but not sure if the logic is proper and also having issues returning variable from the threaded function. I tried two methods by defining it as a separate class as well as a separate function but none of them worked.

Here is my code and specific problem location is between lines 134 ~ 170 and the class method is in lines 60 ~ 82.

import tkinter as tk
from tkinter import ttk,filedialog,messagebox,simpledialog,BOTH,END,LEFT
import threading, time
import pandas as pd
import os
#import Queue
import sys

import win32api



sys.setrecursionlimit(1500)
pd.set_option("display.max_colwidth", 10000)
pd.set_option('display.max_columns', 15)
pd.set_option('precision', 8)

TITLE_FONT = ("Arial",14)
LARGE_FONT = ("Times New Roman",11)


class HardDiskContent(tk.Tk):
    
    def __init__(self, *args, **kwargs):
        
        tk.Tk.__init__(self, *args, **kwargs)
        
        tk.Tk.wm_title(self,"HDD Content Reader")
        
        container = tk.Frame(self)
        container.pack(side="top", fill="both", expand=True)
        container.grid_rowconfigure(0,weight=1)
        container.grid_columnconfigure(0,weight=1)
        
        self.SystemParam = {
                "DriveLetter":tk.StringVar(),
                "SaveFile":tk.StringVar()}
        
        # Store different page information. Add here new page for initialization
        self.frames = {}
        
#        for F in (StartPage,GeneralParameters):
        F = StartPage    
        frame = F(container,self)
        self.frames[F] = frame
        frame.grid(row=0,column=0,sticky="nsew")
        
        self.show_frame(StartPage)
    # Function for showing a frame    
    def show_frame(self,cont):
        frame = self.frames[cont]
        frame.tkraise()
        frame.update()
        frame.event_generate("<<ShowFrame>>")
    
        
    def get_page(self, page_class):
        return self.frames[page_class]
    
class Threader(threading.Thread):

    def __init__(self, Drive_letter):

        threading.Thread.__init__(self, Drive_letter)
        self.daemon = True
        self.Drive_letter = Drive_letter

    def run(self):

#         while True:
#        print("Look a while true loop that doesn't block the GUI!")
        print("Scanning Drive: ",self.Drive_letter)
#        time.sleep(1)
        
        directory_list = []
        
        for (dirpath, dirnames, filenames) in os.walk(self.Drive_letter):
            for k in range(1):
                directory_list.append(dirpath)
        
        print(directory_list)        
        return directory_list
    
    
class StartPage(tk.Frame):
    # Initialization loop. Anything declared here is executed as soon as the program is run. Even if the page is not visible
    def __init__(self,parent,controller):
        tk.Frame.__init__(self,parent)
        self.controller=controller
        # Label for start Page
        label = tk.Label(self, text=" Sakata Lab ",font=TITLE_FONT)
        label.pack(pady=10,padx=10)
                        
       
        top_frame = tk.LabelFrame(self,text="Selection",padx=5,pady=5)
        
        label0 = tk.Label(top_frame, text="Select Drive")
        label0.grid(row=1,column=1,columnspan=2)
        
        label1 = tk.Label(top_frame, text="Save FileName")
        label1.grid(row=2,column=1,columnspan=2)
        
        
        button = tk.Button(top_frame, text="Scan", command =lambda: [self.scan(controller)])
        button.grid(row=1,column=5,columnspan=2,padx=10,pady=5)
        
        drives = win32api.GetLogicalDriveStrings()
        drives = drives.split('\000')[:-1]
#        drives = [drivestr in drives.split('\000') if drivestr]
        print(drives)
        
        self.drive_selection = ttk.Combobox(top_frame,values=drives,height=4,width=10)
        self.drive_selection.grid(row=1, column=3,columnspan=2)
        self.drive_selection.bind("<<ComboboxSelected>>", self.Drive_letter)
        
        self.entry2 = tk.Entry(top_frame, textvariable=self.controller.SystemParam["SaveFile"],width=20)
        self.entry2.grid(row=2,column=3,columnspan=2)
        
      
        button2 = tk.Button(top_frame, text="Save", command =lambda: [self.save_data(controller)])
        button2.grid(row=2,column=5,columnspan=2,padx = 10)

        ## LAYOUT
        top_frame.pack()

        
    def Drive_letter(self,event):
        try:
            self.controller.SystemParam["DriveLetter"] = self.drive_selection.get()
            print("Selected Drive Letter = ", self.controller.SystemParam["DriveLetter"]) 
        except:
            messagebox.showwarning("Drive Selection Notification","No Option Selected")
            
    def Drive_Scanner(self,Drive_letter):
        
        print("Scanning Drive: ",Drive_letter)
        directory_list = []
        
        for (dirpath, dirnames, filenames) in os.walk(self.Drive_letter):
            for k in range(1):
                directory_list.append(dirpath)
        
        self.directory_list = directory_list
#        print(directory_list)        
#        return directory_list
        
        
       
    # Function to notify the user of selection     
    def scan(self,controller):
        
        if not self.drive_selection.get():
            print("Drive Not Selected")
        else:
            print(self.controller.SystemParam["DriveLetter"])
            
            Scan_Process = threading.Thread(target = self.Drive_Scanner,args = self.controller.SystemParam["DriveLetter"])
            Scan_Process.daemon = True
            Scan_Process.start()
            
            directory_list = self.controller.directory_list
            print(directory_list)
#            directory_list = []
#    #        file_list_test = []
#    
#            for (dirpath, dirnames, filenames) in os.walk(self.controller.SystemParam["DriveLetter"]):
#                for k in range(1):
#    #            for dir in dirpath:
#    #                f_test.append(dir)
#                    directory_list.append(dirpath)
##                    print(dirpath)
#    #                file_list_test.append(os.path.join(dirpath+"\\"+dir))
            info = win32api.GetVolumeInformation(self.controller.SystemParam["DriveLetter"])
            print( "disk serial number = %d" % info[1])
            directory_list.insert(0,info[1])
            directory_list.insert(0,info[0])
            print(pd.DataFrame(directory_list))
            
            self.new_data = directory_list
            
            messagebox.showinfo("Scan Complete","Selected drive scanned successfully!")
        
    def set_save_filepath(self,controller):

#        print(self.CableDatabase_Entry.index("end"))
        try:
            self.entry2.delete(0, END)
            filepath = filedialog.askopenfilename(initialdir = "/",title = "Open file for Database",filetypes = (("xlsx files","*.xlsx"),("all files","*.*")))
            self.controller.SystemParam["SaveFile"] = filepath
            print(self.controller.SystemParam["SaveFile"])
            self.entry2.insert(END, filepath)
        except:
            self.entry2.insert(END, "There was an error opening ")
            self.entry2.insert(END, filepath)
            self.entry2.insert(END, "\n")
            
        self.save_data(controller)
                    
    def save_data(self,controller):
        
        if not self.controller.SystemParam["SaveFile"].get():
            messagebox.showwarning("File Name Missing","File Name not entered")
        else:
            filename = self.controller.SystemParam["SaveFile"].get()
            print(filename)
       
            directory_list = pd.DataFrame(self.new_data)
            directory_list.to_csv(filename,header=None,index=False)
            messagebox.showinfo("Save Successful","Directory Names saved successfully!")
            
            
app = HardDiskContent()
app.geometry("600x200") 
app.mainloop()

The errors I am getting are

Error:
TypeError: Drive_Scanner() takes 2 positional arguments but 4 were given
Exception in Tkinter callback

AttributeError: '_tkinter.tkapp' object has no attribute 'directory_list'

Any help or suggestion would be appreciated. I am new to python and tkinter, kindly be gentle with your reply if the issue seems too naive for posting in this forum.

[nilamo]

TypeError: Drive_Scanner() takes 2 positional arguments but 4 were given

Your function only has two params: a reference to the object (self), and the DriveLetter. But when the callback is triggered, tkinter is passing extra arguments, which is throwing an error. So the first step, is taking a peek at what else is getting passed, so you can handle it properly.

The easy way of doing so, is adding *args to the function definition, and then printing it out so you can see what's there.

The second error, about the directory_list, I'd rather see the entire error before commenting on. But it looks like you're trying to use a variable before creating it.

[AvisPaul1]

Thanks for your prompt reply and suggestion. It seems that when I was passing the drive letter eg. 'K:\\' it was treating the variables as K, :, \\ separately. Now I am passing the variable differently and not getting the first error anymore. However the second error remains. The lines in the code from 134 to 157 are modified to

def Drive_Scanner(self,*args):
        
        print('Extra Arguments ',args)
#        print("Scanning Drive: ",Drive_letter)
        print(self.controller.SystemParam["DriveLetter"])
        directory_list = []
        
        for (dirpath, dirnames, filenames) in os.walk(self.controller.SystemParam["DriveLetter"]):
            for k in range(1):
                directory_list.append(dirpath)
        
#        self.directory_list = directory_list
#        print(directory_list)        
        return directory_list
               
       
    # Function to notify the user of selection     
    def scan(self,controller):
        
        if not self.drive_selection.get():
            print("Drive Not Selected")
        else:
#            print(self.controller.SystemParam["DriveLetter"])
            
            Scan_Process = threading.Thread(target = self.Drive_Scanner)

The error that I am getting now is

Error:
Exception in Tkinter callback
Traceback (most recent call last):
  File "D:\Anaconda3\lib\tkinter\__init__.py", line 1705, in __call__
    return self.func(*args)
  File "C:/Users/SakataWoolley/Desktop/Hard Disk GUI/HDDApp3.py", line 112, in <lambda>
    button = tk.Button(top_frame, text="Scan", command =lambda: [self.scan(controller)])
  File "C:/Users/SakataWoolley/Desktop/Hard Disk GUI/HDDApp3.py", line 172, in scan
    directory_list = self.controller.directory_list
  File "D:\Anaconda3\lib\tkinter\__init__.py", line 2101, in __getattr__
    return getattr(self.tk, attr)
AttributeError: '_tkinter.tkapp' object has no attribute 'directory_list'

Kindly let me know how to go about this. Please note the line number mentioned in the error and the code that I posted may not match but should be close by.

[Denni]

I might be wrong here because I have been dealing with the PyQt5 QThread but I am going to guess that the Python Thread should not be sub-classed either so you might want to check that out as well.