如何在 python 中使用按钮作为输入

Question

我需要创建一个程序来计算汽车在已知距离 (100m) 内的速度。我需要程序在用户按下Enter时开始计时（这是模拟汽车进入监控路段时），当用户按下Enter时停止计时 再次计算汽车的平均速度。

Answer 1

begin timing when the user presses Enter (this is supposed to simulate when the car enters the monitored road section), stop timing when the user presses Enter again, then calculate the car's average speed.

CLI 版本：

#!/usr/bin/env python3
from time import monotonic as timer

input("Press Enter to start timer") # wait for the first Enter from the user
start = timer()
input("Press Enter to stop timer")
elapsed = timer() - start
print("Speed {speed:f} m/s".format(speed=100 / elapsed))

要创建 GUI 秒表，您可以使用 tkinter:

#!/usr/bin/env python3
from time import monotonic as timer
from tkinter import font, Tk, ttk

distance = 100 # meters
START, STOP = 'start', 'stop'

class Stopwatch(object):
    def __init__(self, parent):
        self.parent = parent
        # create a button, run `.toggle_button` if it is pressed
        self.button = ttk.Button(parent,text=START, command=self.toggle_button)
        self.button.grid(sticky='nwse') # lays out the button inside the parent

    def toggle_button(self, event=None):
        if self.button is None: # close parent window
            self.parent.destroy()
        elif self.button['text'] == START: # start timer
            self.start = timer()
            self.button['text'] = STOP
        elif self.button['text'] == STOP: # stop timer, show result
            elapsed = timer() - self.start
            self.button.destroy()
            self.button = None
            text = "Speed {:.2f} m/s".format(distance / elapsed)
            ttk.Label(self.parent, text=text, anchor='center').grid()

root = Tk() # create root window
root.protocol("WM_DELETE_WINDOW", root.destroy)  # handle root window deletion
root.bind('<Return>', Stopwatch(root).toggle_button) # handle <Enter> key
root.mainloop()

您可以同时按 Enter 和单击按钮调用 .toggle_button() 方法。

要使主 window 变大，请在 root = Tk() 行之后添加：

root.title('Stopwatch') # set window title
root.geometry('400x300') # set window size
root.columnconfigure(0, weight=1) # children widgets may fill the whole space
root.rowconfigure(0, weight=1)
font.nametofont('TkDefaultFont').configure(size=25) # change default font size

如何在 python 中使用按钮作为输入

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