I am trying to extend the ttk combobox class to allow autosuggestion. the code I have far works well, but I would like to get it to show the dropdown once some text has been entered without removing focus from the entry part of the widget.

The part I am struggling with is finding a way to force the dropdown, in the python docs I cannot find any mention of this, however in the tk docs I did find a post method I believe is supposed to do this, except it doesn't seem to be implemented in the python wrapper.

I also tried generating a down arrow key event once the autosuggest has taken place, however while this does show the dropdown it removes focus, and trying to set the focus after this event doesn't seem to work either (focus does not return)

Is anyone aware of a function I can use to achieve this?

The code I have is for python 3.3 using only standard libs:

class AutoCombobox(ttk.Combobox):def __init__(self, parent, **options):ttk.Combobox.__init__(self, parent, **options)self.bind("<KeyRelease>", self.AutoComplete_1)self.bind("<<ComboboxSelected>>", self.Cancel_Autocomplete)self.bind("<Return>", self.Cancel_Autocomplete)self.autoid = Nonedef Cancel_Autocomplete(self, event=None):self.after_cancel(self.autoid) def AutoComplete_1(self, event):if self.autoid != None:self.after_cancel(self.autoid)if event.keysym in ["BackSpace", "Delete", "Return"]:returnself.autoid = self.after(200, self.AutoComplete_2)def AutoComplete_2(self):data = self.get()if data != "":for entry in self["values"]:match = Truetry:for index in range(0, len(data)):if data[index] != entry[index]:match = Falsebreakexcept IndexError:match = Falseif match == True:self.set(entry)self.selection_range(len(data), "end")self.event_generate("<Down>",when="tail")self.focus_set()breakself.autoid = None

A workaround that achieves this UX using tooltips is demonstrated below. This is implemented using PySimpleGUI, but should be easily adaptable to "pure" tkinter.

from functools import partial
from typing import Callable, Anyfrom fuzzywuzzy import process, fuzz
import PySimpleGUI as sg# SG: Helper functions:
def clear_combo_tooltip(*_, ui_handle: sg.Element, **__) -> None:if tt := ui_handle.TooltipObject:tt.hidetip()ui_handle.TooltipObject = Nonedef show_combo_tooltip(ui_handle: sg.Element, tooltip: str) -> None:ui_handle.set_tooltip(tooltip)tt = ui_handle.TooltipObjecttt.y += 40tt.showtip()def symbol_text_updated(event_data: dict[str, Any], all_values: list[str], ui_handle: sg.Element) -> None:new_text = event_data[ui_handle.key]if new_text == '':ui_handle.update(values=all_values)returnmatches = process.extractBests(new_text, all_values, scorer=fuzz.ratio, score_cutoff=40)sym = [m[0] for m in matches]ui_handle.update(new_text, values=sym)# tk.call('ttk::combobox::Post', ui_handle.widget)  # This opens the list of options, but takes focusclear_combo_tooltip(ui_handle=ui_handle)show_combo_tooltip(ui_handle=ui_handle, tooltip="\n".join(sym))# Prepare data:
all_symbols = ["AAPL", "AMZN", "MSFT", "TSLA", "GOOGL", "BRK.B", "UNH", "JNJ", "XOM", "JPM", "META", "PG", "NVDA", "KO"]# SG: Layout
sg.theme('DarkAmber')
layout = [[sg.Text('Symbol:'),sg.Combo(all_symbols, enable_per_char_events=True, key='-SYMBOL-')]
]# SG: Window
window = sg.Window('Symbol data:', layout, finalize=True)
window['-SYMBOL-'].bind("<Key-Down>", "KeyDown")# SG: Event loop
callbacks: dict[str: Callable] = {'-SYMBOL-': partial(symbol_text_updated, all_values=all_symbols, ui_handle=window['-SYMBOL-']),'-SYMBOL-KeyDown': partial(clear_combo_tooltip, ui_handle=window['-SYMBOL-']),
}
unhandled_event_callback = partial(lambda x: print(f"Unhandled event key: {event}. Values: {x}"))while True:event, values = window.read()if event in (sg.WIN_CLOSED, 'Exit'):breakcallbacks.get(event, unhandled_event_callback)(values)# SG: Cleanup
window.close()

This solution was inspired by this gist and this discussion.