在 Tkinter 中交换

Question

我有一个简单的 Python Tkinter 程序，可以将英尺转换为米。它有一个标签、一个英尺输入框、一个带有凹陷边框的米框，以及 3 个按钮：退出、隐藏和交换。

我只是想弄清楚如何让“交换”按钮做到这一点。交换窗口中“英尺”和“米”的位置，这样您就可以输入 x 米，它会将其转换为英尺（点击“转换”后）。

真的，我所需要的只是如何切换位置（数学部分很简单），但我只是想不出逻辑是如何实现的。这是我到目前为止所得到的：（

import Tkinter

win = Tkinter.Tk()
win.title('Converter')

Row1 =Tkinter.Frame(win)
blank = Tkinter.Label(Row1, text=' ', font=('Courier New', 30))
blank.pack()
Row1.pack()

label = Tkinter.Label(win, text='Convert Between Feet and Meters', font=('Courier
New',30,"bold"))
label.pack()

def convert():
    st = entry1.get()
    v = eval(st)
    if type(v) != type('Hello'):
        answer.config(text=str(v*.3048))

def swap():
    #here's where I need to figure out how to swap


Row2 = Tkinter.Frame(win)
fLabel = Tkinter.Label(Row2, text='Feet', justify='right', font=('Courier New', 30))
entry1 = Tkinter.Entry(Row2, width = 12, font=('Courier New', 30))
fLabel.pack(side='left')
entry1.pack(side='right')
Row2.pack()

Row3 = Tkinter.Frame(win)
mLabel = Tkinter.Label(Row3, text='Meters', justify='right', font=('Courier New',30))
answer = Tkinter.Label(Row3, text='0', width=12, relief='sunken', font=('Courier New',
30))
mLabel.pack(side='left')
answer.pack(side='left')
Row3.pack()

Row4 = Tkinter.Frame(win)
quit = Tkinter.Button(Row4, text='Quit', command = win.destroy, font=('Courier
New',30))
convert = Tkinter.Button(Row4, text='Convert', command = convert, font=('Courier
New',30))
swap = Tkinter.Button(Row4, text='Swap', command=swap, font=('Courier New',30))
quit.pack(side='left')
convert.pack(side='left')
swap.pack(side='right')
Row4.pack()

Row5 = Tkinter.Frame(win)
blank2 = Tkinter.Label(Row5, text=' ', font=('Courier New', 30))
blank2.pack()
Row5.pack()

win.mainloop()

第一帧和最后一帧只是空格填充）提前感谢您的任何帮助！

Answer 1

创建一个变量来存储要转换的内容，并让 swap 函数更改该变量并更新标签。要更改标签的文本，您可以执行 label['text'] = 'new text' 或 label.configure(text='new text')。这是对您的代码的有效修改：

import Tkinter

inputmode = 'feet' # This is the variable that stores what you are converting from


win = Tkinter.Tk()
win.title('Converter')

Row1 =Tkinter.Frame(win)
blank = Tkinter.Label(Row1, text=' ', font=('Courier New', 30))
blank.pack()
Row1.pack()

label = Tkinter.Label(win, text='Convert Between Feet and Meters', font=('Courier New',30,"bold"))
label.pack()

def convert():
    st = entry1.get()
    v = eval(st)
    if type(v) != type('Hello'):
        if inputmode == 'feet': # check which way to convert
            answer.config(text=str(v*.3048))
        else:
            answer.config(text=str(v*3.28))

def swap():
    global inputmode
    if inputmode == 'meters':
        inputmode = 'feet'
        fLabel['text'] = 'Feet' # Changes the text of the label
        mLabel['text'] = 'Metres'
    else:
        inputmode = 'meters'
        fLabel['text'] = 'Metres'
        mLabel['text'] = 'Feet'


Row2 = Tkinter.Frame(win)
fLabel = Tkinter.Label(Row2, text='Feet', justify='right', font=('Courier New', 30))
entry1 = Tkinter.Entry(Row2, width = 12, font=('Courier New', 30))
fLabel.pack(side='left')
entry1.pack(side='right')
Row2.pack()

Row3 = Tkinter.Frame(win)
mLabel = Tkinter.Label(Row3, text='Meters', justify='right', font=('Courier New',30))
answer = Tkinter.Label(Row3, text='0', width=12, relief='sunken', font=('Courier New', 30))
mLabel.pack(side='left')
answer.pack(side='left')
Row3.pack()

Row4 = Tkinter.Frame(win)
quit = Tkinter.Button(Row4, text='Quit', command = win.destroy, font=('Courier New',30))
convert = Tkinter.Button(Row4, text='Convert', command = convert, font=('Courier New',30))
swap = Tkinter.Button(Row4, text='Swap', command=swap, font=('Courier New',30))
quit.pack(side='left')
convert.pack(side='left')
swap.pack(side='right')
Row4.pack()

Row5 = Tkinter.Frame(win)
blank2 = Tkinter.Label(Row5, text=' ', font=('Courier New', 30))
blank2.pack()
Row5.pack()

win.mainloop()

Answer 2

带下标的表比将选择硬连接到代码中更具可扩展性。下面使用下标 t0 和 t1 来索引标签表（英尺、米）和换算系数表（.3048、3.2808）。如果您想创建其他转换，例如摄氏度到华氏度，您可以添加到表中而不更改代码。

其他一些需要注意的事项：

• Pythonic 的交换方式是使用复合赋值 (a,b = b,a) 而不是临时变量 (t=a, a=b, b=t)。
• 任何时候相同的事情重复多次（例如字体规范 - 哇，又大又丑！），请考虑将其设为变量。它既更容易改变，也更紧凑。
• 无需创建空白框架来进行间距，只需使用填充
• 网格布局即可使英尺/米标签/值整齐排列。

以下交换函数使用表/下标方法：

from Tkinter import Tk, Frame, Label, Entry, Button

def convert():
    global t1
    st = entry1.get()
    v = eval(st)
    if type(v) != type('Hello'):
        answer.config(text=str(v*factor[t1]), anchor='w')

def swap():
    global t1, t2
    t1, t2 = t2, t1
    Label1.config(text=lbl[t1])
    Label2.config(text=lbl[t2])
    answer.config(text='')

win = Tk()
win.title('Converter')
fspec = ('Courier New', 30)

label = Label(win, text='Convert Between Feet and Meters', font=fspec+('bold',))
label.pack(pady=30)

Row2 = Frame(win)
Row2.pack()
t1, t2 = 0, 1
lbl = ('Feet', 'Meters')
factor = (.3048, 1./.3048)
Label1 = Label(Row2, text=lbl[t1], justify='right', font=fspec)
entry1 = Entry(Row2, width = 12, font=fspec)
Label2 = Label(Row2, text=lbl[t2], justify='right', font=fspec)
answer = Label(Row2, width=12, relief='sunken', font=fspec)
Label1.grid(row=2, column=2)
entry1.grid(row=2, column=4)
Label2.grid(row=4, column=2)
answer.grid(row=4, column=4)

Row4 = Frame(win)
quitb = Button(Row4, text='Quit', command = win.destroy, font=fspec)
convert = Button(Row4, text='Convert', command = convert, font=fspec)
swap = Button(Row4, text='Swap', command=swap, font=fspec)
quitb.pack(side='left')
convert.pack(side='left')
swap.pack(side='right')
Row4.pack(pady=30)

win.mainloop()