Question

我在Python中有一个简单的Tkinter程序，可将英尺转换为米。它有一个Label，一个Feet Entry框，一个带凹陷边框的Meters框，然后是3个按钮：Quit，Covert和Swap。

我只是想弄清楚如何让Swap按钮做到这一点。在窗口中交换英尺和米的位置，这样您就可以输入x米并将其转换为英尺（在点击转换后）。

真的，我所需要的只是如何切换位置（数学部分很容易），但我想不出逻辑是如何工作的。这是我到目前为止所做的：

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间填充）提前感谢您的帮助！

Answer 1

创建一个存储转换内容的变量，并让swap函数更改变量并更新标签。要更改标签文字，您可以label['text'] = 'new text'或label.configure(text='new text')。以下是对代码的修改：

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

带有下标的表格比代码中的硬连线选择更具扩展性。以下使用下标t0和t1来索引标签表（英尺，米）和转换因子表（.3048,3.2808）。如果您想创建额外的转换，例如摄氏到华氏，您可以在不更改代码的情况下添加到表中。

其他一些注意事项：

交换的pythonic方法是使用复合赋值（a，b = b，a）而不是临时变量（t = a，a = b，b = t）。
任何时候同样的事情会重复多次（例如字体规范 - WOW那么大而丑陋！），考虑将其变为变量。它更容易改变，更紧凑。
不需要为间距创建空白帧，只需使用填充
网格布局使脚/米标签/值清晰排列。

以下交换函数使用table / subscript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()

在Tkinter交换

2 个答案: