estoy usandoesta Código para crear un calendario simple en mi Tkinter. Cuando coloco un calendario en mi ventana raíz principal, el calendario se ve bien. Entonces, decidí poner otro botón que creará una ventana de nivel superior Tkinter y pondré 1 calendario más en la ventana de nivel superior. Pero esta vez no se pudo mostrar el calendario y en su lugar me dio este error" TclError: can't pack .18913120 inside .18912200.18912400". ¿Alguien podría explicar por qué recibo este mensaje de error?

Este es mi código de ejemplo:

import calendar
import sys
try:
    import Tkinter
    import tkFont
except ImportError: # py3k
    import tkinter as Tkinter
    import tkinter.font as tkFont

import ttk

def get_calendar(locale, fwday):
    # instantiate proper calendar class
    if locale is None:
        return calendar.TextCalendar(fwday)
    else:
        return calendar.LocaleTextCalendar(fwday, locale)

class Calendar(ttk.Frame):
    # XXX ToDo: cget and configure

    datetime = calendar.datetime.datetime
    timedelta = calendar.datetime.timedelta

    def __init__(self, master=None, **kw):
        """
        WIDGET-SPECIFIC OPTIONS

        locale, firstweekday, year, month, selectbackground,
        selectforeground
        """
        # remove custom options from kw before initializating ttk.Frame
        fwday = kw.pop('firstweekday', calendar.MONDAY)
        year = kw.pop('year', self.datetime.now().year)
        month = kw.pop('month', self.datetime.now().month)
        locale = kw.pop('locale', None)
        sel_bg = kw.pop('selectbackground', '#ecffc4')
        sel_fg = kw.pop('selectforeground', '#05640e')

        self._date = self.datetime(year, month, 1)
        self._selection = None # no date selected

        ttk.Frame.__init__(self, master, **kw)

        self._cal = get_calendar(locale, fwday)

        self.__setup_styles()       # creates custom styles
        self.__place_widgets()      # pack/grid used widgets
        self.__config_calendar()    # adjust calendar columns and setup tags
        # configure a canvas, and proper bindings, for selecting dates
        self.__setup_selection(sel_bg, sel_fg)

        # store items ids, used for insertion later
        self._items = [self._calendar.insert('', 'end', values='')
                            for _ in range(6)]
        # insert dates in the currently empty calendar
        self._build_calendar()

        # set the minimal size for the widget
        self._calendar.bind('<Map>', self.__minsize)

    def __setitem__(self, item, value):
        if item in ('year', 'month'):
            raise AttributeError("attribute '%s' is not writeable" % item)
        elif item == 'selectbackground':
            self._canvas['background'] = value
        elif item == 'selectforeground':
            self._canvas.itemconfigure(self._canvas.text, item=value)
        else:
            ttk.Frame.__setitem__(self, item, value)

    def __getitem__(self, item):
        if item in ('year', 'month'):
            return getattr(self._date, item)
        elif item == 'selectbackground':
            return self._canvas['background']
        elif item == 'selectforeground':
            return self._canvas.itemcget(self._canvas.text, 'fill')
        else:
            r = ttk.tclobjs_to_py({item: ttk.Frame.__getitem__(self, item)})
            return r[item]

    def __setup_styles(self):
        # custom ttk styles
        style = ttk.Style(self.master)
        arrow_layout = lambda dir: (
            [('Button.focus', {'children': [('Button.%sarrow' % dir, None)]})]
        )
        style.layout('L.TButton', arrow_layout('left'))
        style.layout('R.TButton', arrow_layout('right'))

    def __place_widgets(self):
        # header frame and its widgets
        hframe = ttk.Frame(self)
        lbtn = ttk.Button(hframe, style='L.TButton', command=self._prev_month)
        rbtn = ttk.Button(hframe, style='R.TButton', command=self._next_month)
        self._header = ttk.Label(hframe, width=15, anchor='center')
        # the calendar
        self._calendar = ttk.Treeview(show='', selectmode='none', height=7)

        # pack the widgets
        hframe.pack(in_=self, side='top', pady=4, anchor='center')
        lbtn.grid(in_=hframe)
        self._header.grid(in_=hframe, column=1, row=0, padx=12)
        rbtn.grid(in_=hframe, column=2, row=0)
        self._calendar.pack(in_=self, expand=1, fill='both', side='bottom')

    def __config_calendar(self):
        cols = self._cal.formatweekheader(3).split()
        self._calendar['columns'] = cols
        self._calendar.tag_configure('header', background='grey90')
        self._calendar.insert('', 'end', values=cols, tag='header')
        # adjust its columns width
        font = tkFont.Font()
        maxwidth = max(font.measure(col) for col in cols)
        for col in cols:
            self._calendar.column(col, width=maxwidth, minwidth=maxwidth,
                anchor='e')

    def __setup_selection(self, sel_bg, sel_fg):
        self._font = tkFont.Font()
        self._canvas = canvas = Tkinter.Canvas(self._calendar,
            background=sel_bg, borderwidth=0, highlightthickness=0)
        canvas.text = canvas.create_text(0, 0, fill=sel_fg, anchor='w')

        canvas.bind('<ButtonPress-1>', lambda evt: canvas.place_forget())
        self._calendar.bind('<Configure>', lambda evt: canvas.place_forget())
        self._calendar.bind('<ButtonPress-1>', self._pressed)

    def __minsize(self, evt):
        width, height = self._calendar.master.geometry().split('x')
        height = height[:height.index('+')]
        self._calendar.master.minsize(width, height)

    def _build_calendar(self):
        year, month = self._date.year, self._date.month

        # update header text (Month, YEAR)
        header = self._cal.formatmonthname(year, month, 0)
        self._header['text'] = header.title()

        # update calendar shown dates
        cal = self._cal.monthdayscalendar(year, month)
        for indx, item in enumerate(self._items):
            week = cal[indx] if indx < len(cal) else []
            fmt_week = [('%02d' % day) if day else '' for day in week]
            self._calendar.item(item, values=fmt_week)

    def _show_selection(self, text, bbox):
        """Configure canvas for a new selection."""
        x, y, width, height = bbox

        textw = self._font.measure(text)

        canvas = self._canvas
        canvas.configure(width=width, height=height)
        canvas.coords(canvas.text, width - textw, height / 2 - 1)
        canvas.itemconfigure(canvas.text, text=text)
        canvas.place(in_=self._calendar, x=x, y=y)

    # Callbacks

    def _pressed(self, evt):
        """Clicked somewhere in the calendar."""
        x, y, widget = evt.x, evt.y, evt.widget
        item = widget.identify_row(y)
        column = widget.identify_column(x)

        if not column or not item in self._items:
            # clicked in the weekdays row or just outside the columns
            return

        item_values = widget.item(item)['values']
        if not len(item_values): # row is empty for this month
            return

        text = item_values[int(column[1]) - 1]
        if not text: # date is empty
            return

        bbox = widget.bbox(item, column)
        if not bbox: # calendar not visible yet
            return

        # update and then show selection
        text = '%02d' % text
        self._selection = (text, item, column)
        self._show_selection(text, bbox)

    def _prev_month(self):
        """Updated calendar to show the previous month."""
        self._canvas.place_forget()

        self._date = self._date - self.timedelta(days=1)
        self._date = self.datetime(self._date.year, self._date.month, 1)
        self._build_calendar() # reconstuct calendar

    def _next_month(self):
        """Update calendar to show the next month."""
        self._canvas.place_forget()

        year, month = self._date.year, self._date.month
        self._date = self._date + self.timedelta(
            days=calendar.monthrange(year, month)[1] + 1)
        self._date = self.datetime(self._date.year, self._date.month, 1)
        self._build_calendar() # reconstruct calendar

    # Properties

    @property
    def selection(self):
        """Return a datetime representing the current selected date."""
        if not self._selection:
            return None

        year, month = self._date.year, self._date.month
        return self.datetime(year, month, int(self._selection[0]))


def myfunction():
    root2=Tkinter.Toplevel(root)
    ttkcal = Calendar(root2,firstweekday=calendar.SUNDAY)
    ttkcal.pack(expand=1, fill='both')

root=Tkinter.Tk()

frame=Tkinter.Frame(root)
frame.pack(side="left")

button=Tkinter.Button(root,text="Top level",command=myfunction)
button.pack(side="right")

ttkcal = Calendar(frame,firstweekday=calendar.SUNDAY)
ttkcal.pack(expand=1, fill='both')
root.mainloop()