Changing source file while program is running

Question

I am trying to change a program's behaviour on the fly by editing its source file (under Python 3.4.2, Windows 8.1). My program is a tkinter GUI with a button that sums two values, but I want to be able to change the button's behaviour. I am currently trying to do this by editing the source file (changing, say, the addition to subtraction), saving it, and then clicking a button whose callback function imports the source file. I want my code changes to be reflected in the running GUI without having to exit and restart the program. I also want this import to only recompile the lines that I changed, rather than the entire file.

The program, reload0.py:

import time
import serial
import sys
import os
import tkinter as tk
from tkinter import ttk
from tkinter import *
from tkinter import messagebox
from tkinter import filedialog
try:
  import Tkinter              # Python 2
  import ttk
except ImportError:
  import tkinter as Tkinter   # Python 3
  import tkinter.ttk as ttk
mGui = Tk()
mGui.title("GUI")
mGui.geometry('400x200+100+100')
def mOp():
  num1 = value1.get()
  num2 = value2.get()
  Op=num1+num2
  name1.set('Sum')
  name2.set(Op)
def mReLoad():
  import reload0.py
  mGui.update()
def mCheck():
  if len(name1.get()) == 0:
    name1.set('name1')
    mGui.update()
  if (len(name2.get()) == 0):
    name2.set('name2')
    mGui.update()
  try:
      print(value1.get())
  except ValueError:
      value1.set(0)
      mGui.update()
  try:
      print(value2.get())
  except ValueError as ValE:
      value2.set(0)
      mGui.update()
      print(ValE)

value1 = DoubleVar()
value2 = DoubleVar()
name1 = StringVar()
name2 = StringVar()
mButtonSave = Button(mGui, text = "Operation", command = mOp, fg = 'Red').place(x=150,y=80)
mButtonLoad = Button(mGui, text = "ReLoad Operation", command = mReLoad, fg = 'Red').place(x=150,y=110)
mButtonLoad = Button(mGui, text = "Check", command = mCheck, fg = 'Red').place(x=150,y=140)
tText1 = Entry(mGui, textvariable = name1).place(x=10,y=80)
tText2 = Entry(mGui, textvariable = name2).place(x=10,y=100)
vText1 = Entry(mGui, textvariable = value1).place(x=10,y=120)
vText2 = Entry(mGui, textvariable = value2).place(x=10,y=140)

Answer 1

For your purpose of changing button functionality there are easier ways than changing source code and as commented it's not possible.

Judging from another question of yours, you are quite new to Python programming. I would recommend spending some time on some basic tutorials getting to know Python and some programming concepts first.

For instance:

import reload.py 

Should be:

import reload