不应在for循环中出现值错误？

这是我的代码：

    while counter <= len(titles):
        currenttime = [perc[counter], fails[counter], titles[counter]]
        print(currenttime)
        for percent, fail, title in currenttime:

当我运行它时，出现一个值错误，显示

ValueError: not enough values to unpack (expected 3, got 2)

但是当我打印当前时间时，我得到

['67', '1', 'subsection']

对我来说，这看起来像3个值，但显然我错了，有人可以启发我吗？我环顾四周，但没有发现良好的答案。任何帮助将不胜感激。谢谢

代码上下文：

      n = 0
    perc = list()
    while n < len(piedata):
        perc.append(piedata[n+2])
        n += 3
    print (perc)

    n = 0
    fails = list()
    while n < len(piedata):
        fails.append(piedata[n+1])
        n += 3
    print(fails)

    n = 0
    titles = list()
    while n < len(piedata):
        titles.append(piedata[n])
        n += 3
    print(titles)

    counter = 0
    while counter <= len(titles):
        currenttime = [perc[counter], fails[counter], titles[counter]]
        print(currenttime)
        for percent, fail, title in currenttime:
            piedata = [percent, (100-percent)]

            fig = matplotlib.figure.Figure(figsize=(5, 5))
            ax = fig.add_subplot(111)
            ax.pie(piedata)  # this is the information that the circle diagram will be made out of
            ax.legend([('amount of attempts:', NOTT), ('amount of fails', fail)])

            circle = matplotlib.patches.Circle((0, 0), 0.7, color='white')
            ax.add_artist(circle)


            # this is the code for actually putting the circle diagram/pie chart on the screen
            canvas = FigureCanvasTkAgg(fig, master=window)
            canvas.get_tk_widget().pack()
            canvas.draw()

            Label(window, text=(title, title), bg='light blue').pack()
            counter += 1

            window.mainloop()
            print(percent)
            print(fail)