How stop re-writing log data during program re-run / Python

I having an issue with logging. Every time when i re-run my program it overwrites log data in file as I need to store previous data as well. I have created if statements when there is file it doesn't create a new one as i thought, but it doesn't solved my problem. Maybe someone knows the issue? Thank you in advance!

from tkinter import *
from tkinter import filedialog
import easygui
import shutil
import os
from tkinter import filedialog
from tkinter import messagebox as mb
from pathlib import Path
import logging
from datetime import date


def open_window():
    read=easygui.fileopenbox()
    return read

#logging config

if Path('app.log').is_file():
    print ("File exist")
else:
    logging.basicConfig(filename='app.log', filemode="w", format='%(name)s - %(levelname)s - %(message)s ')
    print ("File doesn't exist and will be created")


LOG_for="%(asctime)s, log content: %(message)s"

logger=logging.getLogger()
logger.setLevel(logging.DEBUG)


# Function for opening the
# file explorer window
def browseFiles():
    filename = filedialog.askopenfilename(initialdir = "/",
                                          title = "Select a File",
                                          filetypes = (("Text files",
                                                        "*.txt*"),
                                                       ("all files",
                                                        "*.*")))
      
    # Change label contents
    label_file_explorer.configure(text="File Opened: "+filename)
      
# move file function
def move_file():
    source = open_window()
    filename = os.path.basename(source)
    destination =filedialog.askdirectory()
    dest = os.path.join(destination,filename)
    if(source==dest):
        mb.showinfo('confirmation', "Source and destination are same, therefore file will be moved to Home catalog")
        newdestination = Path("/home/adminas")
        shutil.move(source, newdestination)
        logging.shutdown()
        #current_time()
        logging.basicConfig(filename='app.log', filemode="w", format=LOG_for) 
        logging.info('File was moved to' + newdestination)
        
    else:
        shutil.move(source, destination)  
        mb.showinfo('confirmation', "File Moved !")
        #current_time()
        logging.basicConfig(filename='app.log', filemode="w", format=LOG_for)
        logging.info('File was moved to' + destination) 
                                                                                                  
# Create the root window
window = Tk()
  
# Set window title
window.title('File Explorer')
  
# Set window size
window.geometry("400x400")
  
#Set window background color
window.config(background = "white")
  
# Create a File Explorer label
label_file_explorer = Label(window,
                            text = "File Explorer using Tkinter",
                            width = 50, height = 4,
                            fg = "blue")
  
      
button_explore = Button(window,
                        text = "Browse Files",
                        command = browseFiles)

button_move = Button(window,
                        text = "Move File",
                        command = move_file)     
  
button_exit = Button(window,
                     text = "Exit",
                     command = exit)
  
# Grid method is chosen for placing
# the widgets at respective positions
# in a table like structure by
# specifying rows and columns
label_file_explorer.grid(column = 1, row = 1)

button_move.grid(column = 1, row = 2)
  
button_exit.grid(column = 1,row = 3)
  
# Let the window wait for any events
logging.shutdown()
window.mainloop()

But in the shell it prints properly, but every time running program over and over again it overwrites as a example new data like this and after re-run it vanishes and being preplaces by new one:

2021-05-02 11:04:15,384, log level: INFO, log content: File was moved to/home/adminas/Documents

Solution

Not quite understand your problem. But if you don't want to overwrite log files, change the filemode to 'a' which will append new log to your log files.