tkinter 中的基本计时器 [英] Basic timer in tkinter

问题描述

我已经为 python 计时器编写了一些代码，但是当我运行它时，我得到一个错误，但问题是我不知道该怎么做，所以我在互联网上搜索了所有帮助后来到这里寻求帮助，但是我找不到与我的问题相符的内容.

I have written some code for a python timer but when ever I run it I get an error but the thing is I don't know what to do so I came here for help after I searched all over the internet for help but I couldn't find anything that matched my problem.

这里是错误:

Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Program Files\Python33\lib\tkinter\__init__.py", line 1475, in __call__
    return self.func(*args)
  File "C:\Users\Public\Documents\Programming\Timer.py", line 27, in start
    sec = sec + 1
UnboundLocalError: local variable 'sec' referenced before assignment

这是我的代码:

# Import Modules
from tkinter import *
import time

# Window Setup
root = Tk()
root.title('Timer')
root.state('zoomed')

# Timer Variables
global sec
time_sec = StringVar()
sec = 0

# Timer Start
def start():
    while 1:
        time.sleep(1)
        sec = sec + 1
        time_sec.set(sec)
        start()

# Timer Setup
Label(root,
      textvariable=time_sec,
      fg='green').pack()
Button(root,
       fg='blue',
       text='Start',
       command=start).pack()

# Program Loop
root.mainloop()

有人可以帮我吗?

提前致谢！

推荐答案

您必须将 sec 声明为 start 的全局内部.以下是修复错误的方法:

You have to declare sec to be a global inside of start. Here is how to fix the error:

# Import Modules
from tkinter import *
import time

# Window Setup
root = Tk()
root.title('Timer')
root.state('zoomed')

# Timer Variables
global sec
time_sec = StringVar()
sec = 0

# Timer Start
def start():
    while 1:
        time.sleep(1)
        ### You have to declare sec as a global ###
        global sec
        sec = sec + 1
        time_sec.set(sec)
        start()

# Timer Setup
Label(root,
      textvariable=time_sec,
      fg='green').pack()
Button(root,
       fg='blue',
       text='Start',
       command=start).pack()

# Program Loop
root.mainloop()

然而，这仍然有问题，因为它会由于 while 循环而冻结屏幕.使用 tkinter 构建计时器的更好方法是这样的:

However, this still has problems because it freezes the screen due to the while loop. A better way to build a timer with tkinter is like this:

from tkinter import *

root = Tk()
root.title('Timer')
root.state('zoomed')

sec = 0

def tick():
    global sec
    sec += 1
    time['text'] = sec
    # Take advantage of the after method of the Label
    time.after(1000, tick)

time = Label(root, fg='green')
time.pack()
Button(root, fg='blue', text='Start', command=tick).pack()

root.mainloop()

另外，对未来的一些建议:永远不要在 GUI 中使用 time.sleep 或 while 循环.而是利用 GUI 的主循环.它将避免许多令人头疼的事情冻结或崩溃.希望这会有所帮助！

Also, some advice for the future: never use time.sleep or a while loop like that in a GUI. Take advantage of the GUI's mainloop instead. It will save many headaches of stuff freezing or crashing. Hope this helps!

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