Python代码作为模块而不是类

Question

我试图找出原因，但可能不知道正确的问题。我有一个项目，我正在尝试为我的汽车创建仪表板。问题是，当我尝试让另一个类中的画布对象出现时，我的 GUI 启动但不显示任何内容。如果我在不要求画布出现的情况下启动 GUI，则 GUI 工作并显示屏幕。我是 Python 新手。我的版本是 3.5

我的主程序：

from tkinter import*
from helperThingys import Helpers

root = Tk()
root.geometry("800x480")

bgLeft = Frame(root, bg="black", width=200, height=480)
bgLeft.pack_configure(fill=BOTH, expand=1, side=LEFT)
bgMiddle = Frame(root, bg="black", width=400, height=480)
bgMiddle.pack_configure(fill=BOTH, expand=1, side=LEFT)
bgRight = Frame(root, bg="black", width=200, height=480)
bgRight.pack_configure(fill=BOTH, expand=1, side=LEFT)

# These are really gif images read to labels to be able to grid them
# now just plain text labels for convenience. 
label_4hi = Label(bgLeft, text="ok", bg="green")
label_4lo = Label(bgLeft, text="ok", bg="green")
label_lock = Label(bgLeft, text="ok", bg="green")
label_batt = Label(bgMiddle, text="ok", bg="red")
label_fuelF = Label(bgLeft, text="ok", bg="orange")
label_glow = Label(bgLeft, text="ok", bg="yellow")
label_hb = Label(bgMiddle, text="ok", bg="blue")
label_indL = Label(bgMiddle, text="ok", bg="green")
label_indR = Label(bgMiddle, text="ok", bg="green")
label_lowFuel = Label(bgLeft, text="ok", bg="red")
label_lowOil = Label(bgLeft, text="ok", bg="red")
label_park = Label(bgMiddle, text="ok", bg="red")
label_pwrS = Label(bgLeft, text="ok", bg="red")
label_rFog = Label(bgLeft, text="ok", bg="orange")
label_temp = Label(bgLeft, text="ok", bg="red")
label_gauge = Label(bgMiddle, text="ok", bg="red")

# Middle frame
bgMiddle.rowconfigure(0, minsize=46, weight=1)
bgMiddle.rowconfigure(1, minsize=217, weight=5)
bgMiddle.rowconfigure(2, minsize=217, weight=5)
bgMiddle.columnconfigure(0, minsize=80)
bgMiddle.columnconfigure(1, minsize=80)
bgMiddle.columnconfigure(2, minsize=80)
bgMiddle.columnconfigure(3, minsize=80)
bgMiddle.columnconfigure(4, minsize=80)

label_indL.grid(row=0, column=0, sticky=E+N+W)
label_hb.grid(row=0, column=1, sticky=E+N+S+W)
label_park.grid(row=0, column=2, sticky=E+N+S+W)
label_batt.grid(row=0, column=3, sticky=E+N+S+W)
label_indR.grid(row=0, column=4, sticky=E+N+S+W)

# Left frame
bgLeft.rowconfigure(0, minsize=46, weight=1)
bgLeft.rowconfigure(1, minsize=46, weight=1)
bgLeft.rowconfigure(2, minsize=46, weight=1)
bgLeft.rowconfigure(3, minsize=46, weight=1)
bgLeft.rowconfigure(4, minsize=46, weight=1)
bgLeft.columnconfigure(0, minsize=100)
bgLeft.columnconfigure(1, minsize=100)

label_4hi.grid(row=0, column=0, sticky=E+N+S+W)
label_4lo.grid(row=0, column=1, sticky=E+N+S+W)
label_lock.grid(row=1, column=0, sticky=E+N+S+W)
label_pwrS.grid(row=1, column=1, sticky=E+N+S+W)
label_rFog.grid(row=2, column=0, sticky=E+N+S+W)
label_lowFuel.grid(row=2, column=1, sticky=E+N+S+W)
label_lowOil.grid(row=3, column=0, sticky=E+N+S+W)
label_temp.grid(row=3, column=1, sticky=E+N+S+W)
label_fuelF.grid(row=4, column=0, sticky=E+N+S+W)
label_glow.grid(row=4, column=1, sticky=E+N+S+W)

# Middle frame
speedo = helpers.Gauge()
speedo.makeGauge(bgMiddle, 150, "speed")
speedo.grid(row=1, columnspan=5, sticky=E+N+S+W)
#label_gauge.grid(row=1, columnspan=5, sticky=E+N+S+W)

# Right Frame

#oilPres = Gauge(bgRight, 150, "oilPres")

root.mainloop()

这里是 helperThingys 包中的“helpers.py”。

from tkinter import Canvas

class Gauge(Canvas):

    def __init__(self):
        Canvas.__init__(self)
        pass

    def makeGauge(self, window, value, gaugeType):
        if gaugeType == "speed":
            baseCanvas = Canvas(window, bg="black", width=400, height=217,
                                highlightthickness=0)
            baseCanvas.create_arc([10, 5, 390, 395], start=0, extent=180,
                                  fill="white")
            return baseCanvas

我使用画布作为仪表的背景。奇怪的是，当它不是一个类而是一个模块时，这个“helpers.py”工作并为我的 GUI 创建了画布：

def makeGauge(self, window, value, gaugeType):
    if gaugeType == "speed":
        baseCanvas = Canvas(window, bg="black", width=400, height=217,
                                highlightthickness=0)
        baseCanvas.create_arc([10, 5, 390, 395], start=0, extent=180,
                                  fill="white")
        return baseCanvas

... 以此类推（该模块与 GUI 位于同一个包中）。这就是为什么我知道画布可以与 GUI 一起使用。在课堂上使用它们时我做错了什么？

感谢您的回答。

Answer 1

您的问题是Gauge 两者都是Canvas 的子类并且 创建一个或多个其他画布（奇怪的是，它们是某个其他窗口的子类）。

当您调用makeGauge 时，这将创建第二个画布并返回它。但是，您不保存引用，并且您永远不会在第二个画布上调用 pack、place 或 grid，因此它永远不会出现。

我不知道你打算用这两张画布做什么，但我猜你真的只想要一张。我建议制作这样的类，在创建画布时传递所有参数，以便您可以一步创建仪表：

class Gauge(Canvas):
    def __init__(self, parent, value, gaugeType):
        Canvas.__init__(self, parent)
        self.makeGauge(value, gaugeType)

    def makeGauge(self, value, gaugeType):
        if gaugeType == "speed":
            self.configure(bg="black", width=400, height=217,
                           highlightthickness=0)
            self.create_arc([10, 5, 390, 395], start=0, extent=180,
                            fill="white")

        elif gaugeType == "rpm":
            ...

speedo = Gauge(bgMiddle, 150, "speed")
speedo.grid(...)

如果你想保留两个画布，或者你决定让Gauge从其他东西继承，你需要保存makeGauge返回的引用，然后将其添加到显示中：

gauge = speedo.makeGauge(bgMiddle, 150, "speed")
gauge.grid(row=1, columnspan=5, sticky=E+N+S+W)