如何在tkinter中显示函数的值

Question

I am new to python and tkinter and I have decided that I will make a stopwatch. I have gooled alot and find many useful information, but I still haven't found how to display value of a function in tkinter. Here is my current code:

import time
from tkinter import*
import os

root = Tk()

def clock(event):
    second = 0
    minute = 0
    hour = 0  
    while True:
        time.sleep(0.99)
        second +=1
        print(hour,":",minute,":",second)
    return

def stop(event):
    time.sleep(1500)

def clear(event):
    os.system('cls')


button1 = Button(root, text="Start")
button2 = Button(root, text="Stop")
button3 = Button(root, text="Clear")

button1.bind("<Button-1>", clock)
button2.bind("<Button-1>", stop)
button3.bind("<Button-1>", clear)

button1.grid(row=2, column=0, columnspan=2)
button2.grid(row=2, column=2, columnspan=2)
button3.grid(row=2, column=4, columnspan=2)


root.mainloop()

I am aware that the code isn't perefect yet(especially the functions stop and clear).

Answer 1

You might consider using callback functions (call your function when something happens? when clicking a button for example)

In Tkinter, a callback is Python code that is called by Tk when something happens. For example, the Button widget provides a command callback which is called when the user clicks the button. You also use callbacks with event bindings.

You can use any callable Python object as a callback. This includes ordinary functions, bound methods, lambda expressions, and callable objects. This document discusses each of these alternatives briefly. Example: To use a function object as a callback, pass it directly to Tkinter.

from Tkinter import *

def callback():
    print "clicked!"

b = Button(text="click me", command=callback)
b.pack()

mainloop()

http://effbot.org/zone/tkinter-callbacks.htm

Answer 2

It's unclear from your sample code which function's value you want to display.

Regardless, a good way to do accomplish something like that in tkinter is by creating instances of its StringVar control class and then specifying them as the textvariable option of another widget. After this is done, any changes to the value of the StringVar instance will automatically update the associated widget's text.

The code below illustrates this:

import os
import time
import tkinter as tk

class TimerApp(tk.Frame):
    def __init__(self, master=None):
        tk.Frame.__init__(self, master=None)
        self.grid()
        self.create_widgets()
        self.elapsed = 0
        self.refresh_timer()
        self.after_id = None  # used to determine and control if timer is running

    def create_widgets(self):
        self.timer = tk.StringVar()
        self.timer.set('')
        self.timer_label = tk.Label(self, textvariable=self.timer)
        self.timer_label.grid(row=1, column=2)

        self.button1 = tk.Button(self, text="Start", command=self.start_clock)
        self.button1.grid(row=2, column=0, columnspan=2)
        self.button2 = tk.Button(self, text="Stop", command=self.stop_clock)
        self.button2.grid(row=2, column=2, columnspan=2)
        self.button3 = tk.Button(self, text="Clear", command=self.clear_clock)
        self.button3.grid(row=2, column=4, columnspan=2)

    def start_clock(self):
        self.start_time = time.time()
        self.after_id = self.after(1000, self.update_clock)

    def stop_clock(self):
        if self.after_id:
            self.after_cancel(self.after_id)
            self.after_id = None

    def clear_clock(self):
        was_running = True if self.after_id else False
        self.stop_clock()
        self.elapsed = 0
        self.refresh_timer()
        if was_running:
            self.start_clock()

    def update_clock(self):
        if self.after_id:
            now = time.time()
            delta_time = round(now - self.start_time)
            self.start_time = now
            self.elapsed += delta_time
            self.refresh_timer()
            self.after_id = self.after(1000, self.update_clock)  # keep updating

    def refresh_timer(self):
        hours, remainder = divmod(self.elapsed, 3600)
        minutes, seconds = divmod(remainder, 60)
        self.timer.set('{:02d}:{:02d}:{:02d}'.format(hours, minutes, seconds))

app = TimerApp()
app.master.title('Timer')
app.mainloop()