include two ttk calendar buttons in GUI window, python 2.7 - python-2.7

Question

I learned how to implement ttk calendar from this post Python Tkinter ttk calendar
All I want is including two ttk calendars button in my GUI interface. One for the 'arrival date' button and another for the 'return date' button. However, after I tried to include these two buttons in my GUI window, my GUI window becomes very laggy and slow to be loaded and it sometimes even freezes. Can someone give me some suggestion on what is the problem here?
Based on the link above, I tried to include on ttk calendar button first and everything works fine and my GUI window works smoothly. However, as long as I have two ttk calendar buttons being included, the whole GUI window is very laggy.
# from stackoverflow
# https://stackoverflow.com/questions/48298195/python-tkinter-ttk-calendar
class MyDateEntry(DateEntry):
def __init__(self, master=None, **kw):
DateEntry.__init__(self, master=master, **kw)
# add black border around drop-down calendar
self._top_cal.configure(bg='black', bd=1)
# add label displaying today's date below
tk.Label(self._top_cal, bg='gray90', anchor='w',
text='Today: %s' % date.today().strftime('%x')).pack(fill='x')
...
...
...
# first button
ttk.Label(self.frame_entry_left_col, text='Arrival Date:').grid(row=6, column=0, padx=5, pady=(5, 0), sticky=tk.W)
self.fldArrivalDate = MyDateEntry(self.color, master=self.frame_entry_left_col, font=("Calibri", 8), background=self.color.secondary, width=17, selectmode='day')
self.fldArrivalDate.grid(row=7, column=0, padx=5, pady=(0, 6))
# second button
ttk.Label(self.frame_entry_left_col, text='Return Date:').grid(row=8, column=0, padx=5, pady=(5, 0), sticky=tk.W)
self.fldReturnDate = MyDateEntry(self.color, master=self.frame_entry_left_col, font=("Calibri", 8), width=17, selectmode='day')
self.fldReturnDate.grid(row=9, column=0, padx=5, pady=(0, 6))
I expect both buttons can work smoothly.

Answer 1

I don't reproduce your slowdown on Windows with Python 3.7. Your example is not really complete enough so what I actually tested is below.
A possible missing cause of the slowup is if you have conflicting pack and grid geometry management in a single frame. We can't see that from the code provided. In the below example you could pack the text widget and see if that causes a problem. In the version of Tkinter with Python 3.7 doing both packa nd grid in the same frame will raise an error but depending on the version of Tk you are using this might not occur on Python 2.7 and at one point this caused a lockup in Tk as the geometry managers fought against each other.
# https://stackoverflow.com/q/56811713/291641
#
# pip install tkcalendar
import sys
import tkinter as tk
import tkinter.ttk as ttk
from tkcalendar import DateEntry
from datetime import date
class MyDateEntry(DateEntry):
def __init__(self, master=None, **kw):
DateEntry.__init__(self, master=master, **kw)
# add black border around drop-down calendar
self._top_cal.configure(bg='black', bd=1)
# add label displaying today's date below
tk.Label(self._top_cal, bg='gray90', anchor='w',
text='Today: %s' % date.today().strftime('%x')).pack(fill='x')
def main(args=None):
root = tk.Tk()
frame = ttk.Frame(root)
row = 0
for name in ['Arrival' , 'Departure']:
label = ttk.Label(frame, text=name + ': ')
cal = MyDateEntry(master=frame, width=17, selectmode='day')
label.grid(row=row, column=0, sticky='news')
cal.grid(row=row, column=1, sticky='news')
row += 1
text = tk.Text(frame)
text.grid(row=row, columnspan=2, sticky='news')
frame.grid_rowconfigure(row, weight=1)
frame.grid_columnconfigure(1, weight=1)
frame.grid(row=0, column=0, sticky='news')
root.grid_rowconfigure(0, weight=1)
root.grid_columnconfigure(0, weight=1)
root.mainloop()
return 0
if __name__ == '__main__':
sys.exit(main(sys.argv[1:]))