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In an attempt to answer How to justify the characters in the drop-down list of a Combobx? I've come up with this code.

JustifiedCombobox justifies the pop-down list's items almost precisely after pop-down list's been first created & customized and then displayed. After the pop-down list's been created, setting self.justify value to a valid one will again, customize the justification almost right after the pop-down list's first been displayed:

try: # In order to be able to import tkinter for
 import tkinter as tk # either in python 2 or in python 3
 from tkinter import ttk
except:
 import Tkinter as tk
 import ttk


class JustifiedCombobox(ttk.Combobox):
 """
 Creates a ttk.Combobox widget with its drop-down list items
 justified with self.justify as late as possible.
 """

 def __init__(self, master, *args, **kwargs):
 ttk.Combobox.__init__(self, master, *args, **kwargs)
 self.justify = 'center'


 def _justify_popdown_list_text(self):
 self._initial_bindtags = self.bindtags()
 _bindtags = list(self._initial_bindtags)
 _index_of_class_tag = _bindtags.index(self.winfo_class())
 # This dummy tag needs to be unique per object, and also needs
 # to be not equal to str(object)
 self._dummy_tag = '_' + str(self)
 _bindtags.insert(_index_of_class_tag + 1, self._dummy_tag)
 self.bindtags(tuple(_bindtags))
 _events_that_produce_popdown = tuple([ '<KeyPress-Down>',
 '<ButtonPress-1>',
 '<Shift-ButtonPress-1>',
 '<Double-ButtonPress-1>',
 '<Triple-ButtonPress-1>',
 ])
 for _event_name in _events_that_produce_popdown:
 self.bind_class(self._dummy_tag, _event_name,
 self._initial_event_handle)


 def _initial_event_handle(self, event):
 _instate = str(self['state'])
 if _instate != 'disabled':
 if event.keysym == 'Down':
 self._justify()
 else:
 _ = self.tk.eval(' identify element '.format(self,
 event.x, event.y))
 __ = self.tk.eval('string match *textarea '.format(_))
 _is_click_in_entry = bool(int(__))
 if (_instate == 'readonly') or (not _is_click_in_entry):
 self._justify()


 def _justify(self):
 self.tk.eval('.popdown.f.l configure -justify '.format(self,
 self.justify))
 self.bindtags(self._initial_bindtags)


 def __setattr__(self, name, value):
 self.__dict__[name] = value
 if name == 'justify':
 self._justify_popdown_list_text()


def select_handle():
 global a
 _selected = a['values'][a.current()]
 if _selected in ("left", "center", "right"):
 a.justify = _selected


if __name__ == '__main__':
 root = tk.Tk()
 for s in ('normal', 'readonly', 'disabled'):
 JustifiedCombobox(root, state=s, values=[1, 2, 3]).grid()
 a = JustifiedCombobox(root, values=["Justify me!", "left", "center", "right"])
 a.current(0)
 a.grid()
 a.bind("<<ComboboxSelected>>", lambda event: select_handle())
 root.mainloop()

Review Concern(s):

• My main concern is to code in an easy to read, efficient, and well-structured manner while still learning the language and concepts in computer science¹ such as OOP. Feel free to mention the tiniest issue or improvement that comes to your mind, as I am a beginner and I probably need it.




• I believe the code should run on both python 3.x and python 2.7, but I have only tested it for python 3.6.3. If the code doesn't work for those other versions, or it can work cross-version like I intended it to be but still could use improvements, please let me know.

¹I haven't a degree in computer science or a very closely related subject.