Python - Multiprocessing vs Multithreading for file-based work - multithreading

Question

I have created a GUI (using wxPython) that allows the user to search for files and their content. The program consists of three parts:
The main GUI window
The searching mechanism (seperate class)
The output window that displays the results of the file search (seperate class)
Currently I'm using pythons threading module to run the searching mechanism (2) in a separate thread, so that the main GUI can still work flawlessly. I'm passing the results during runtime to the output window (3) using Queue. This works fine for less performance requiring file-reading-actions, but as soon as the searching mechanism requires more performance, the main GUI window (1) starts lagging.
This is roughly the schematic:
import threading
import os
import wx
class MainWindow(wx.Frame): # this is point (1)
def __init__(self, parent, ...):
# Initialize frame and panels etc.
self.button_search = wx.Button(self, label="Search")
self.button_search.Bind(wx.EVT_BUTTON, self.onSearch)
def onSearch(self, event):
"""Run filesearch in separate Thread""" # Here is the kernel of my question
filesearch = FileSearch().Run()
searcher = threading.Thread(target=filesearch, args=(args,))
searcher.start()
class FileSearch(): # this is point (2)
def __init__(self):
...
def Run(self, args):
"""Performs file search"""
for root, dirs, files in os.walk(...):
for file in files:
...
def DetectEncoding(self):
"""Detects encoding of file for reading"""
...
class OutputWindow(wx.Frame): # this is point (3)
def __init__(self, parent, ...):
# Initialize output window
...
def AppendItem(self, data):
"""Appends a fileitem to the list"""
...
My questions:
Is python's multiprocessing module better suited for this specific performance requiring job?
If yes, which way of interprocess communication (IPC) should I choose to send the results from the searching mechanism class (2) to the output window (3) and how should implement it schematically?