I need to show a MessageBox to let the user deicide if He wants to overwrite a file.

    # ----------------FILE CREDENTIALS CREATION-----------------------------
    def create_credentials_file(self, samba_user, samba_pass, samba_domain, credentials_filepath):
        """Create the file with credentials in specified path"""
        print("Entering to function create_credentials_file...")
        if os.path.isfile(credentials_filepath):
            self.message_overwrite_credentials(samba_user, samba_pass, samba_domain, credentials_filepath)


    def message_overwrite_credentials(self, samba_user, samba_pass, samba_domain, credentials_filepath):
        """Message box to confirm overwrite"""
        msg_overwrite = QMessageBox.warning(self,"Overwrite Credentials File",
            "File already exists. Do you want to overwrite it?", QMessageBox.Yes | QMessageBox.No)
        if msg_overwrite == QMessageBox.Yes:
            self.write_credentials_file(samba_user, samba_pass, samba_domain, credentials_filepath)
        else:
            self.text_edit.append(" Credentials file not overwritten...")
    
    def write_credentials_file(self, samba_user, samba_pass, samba_domain, credentials_filepath):
        """Create the file with credentials in specified path"""
        with open(credentials_filepath,'w',0o600) as file:
            file.write("username="+samba_user+"n")
            file.write("password="+samba_pass+"n")
            file.write("domain="+samba_domain+"n")
            self.text_edit.append(" Credentials file overwritten...")
            self.button_apply.setEnabled(True)

Then I call the methods like this

def apply_clicked(self):
        """Events when accept button is pushed""" 
        self.button_apply.setEnabled(False)                
        self.text_edit.append("button clicked")   
        QTimer.singleShot(1000, lambda: self.create_credentials_folder(self.samba_path_credentials))
        QTimer.singleShot(1000, lambda: self.create_credentials_file(self.samba_user, self.samba_pass, self.samba_domain, self.credentials_filepath))

I was suggested to use threading, but what is the best approach?