A simple example of creating a new ttk theme

new_ttk_theme.py

"""
  Author: Israel Dryer
  Modified: 2021-04-16
  
  Here's a simple example of creating a new theme with a single custom widget - a modern looking radiobutton.
  In this example, I used a dictionary of settings. However, you can just as well do it with the Style.map, 
  Style.layout, and Style.configure methods. But, if you're going to build an entire theme, then using a settings 
  dictionary is more scalable, and could technically be stored in an offline json file as well.
"""
from PIL import ImageDraw, Image, ImageTk
from tkinter import ttk

style = ttk.Style()

# radio off image
radio_off = Image.new('RGBA', (134, 134))
draw = ImageDraw.Draw(radio_off)
draw.ellipse([2, 2, 132, 132], outline="#adb5bd", width=3, fill="#f8f9fa")
radio_off_img = ImageTk.PhotoImage(radio_off.resize((14, 14), Image.LANCZOS))

# radio on image
radio_on = Image.new('RGBA', (134, 134))
draw = ImageDraw.Draw(radio_on)
draw.ellipse([2, 2, 132, 132], outline="#4582ec", width=12, fill="#4582ec")
draw.ellipse([40, 40, 94, 94], fill="#ffffff")
radio_on_img = ImageTk.PhotoImage(radio_on.resize((14, 14), Image.LANCZOS))

# radio disabled image
radio_disabled = Image.new('RGBA', (134, 134))
draw = ImageDraw.Draw(radio_disabled)
draw.ellipse([2, 2, 132, 132], outline="#c5c7c7", width=3, fill="#f8f9fa")
draw.ellipse([40, 40, 94, 94], fill="#f8f9fa")
radio_disabled_img = ImageTk.PhotoImage(radio_disabled.resize((14, 14), Image.LANCZOS))

# create theme settings
theme_settings = {
    'Radiobutton.indicator': {
        'element create': ('image', radio_on_img,
                           ('disabled', radio_disabled_img),
                           ('!selected', radio_off_img),
                           {'width': 28, 'border': 4, 'sticky': 'w'})},
    'TRadiobutton': {
        'layout': [
            ('Radiobutton.padding', {'children': [
                ('primary.Radiobutton.indicator', {'side': 'left', 'sticky': ''}),
                ('Radiobutton.focus', {'children': [
                    ('Radiobutton.label', {'sticky': 'nswe'})], 'side': 'left', 'sticky': ''})],
                'sticky': 'nswe'})],
        'configure': {
            'background': "#ffffff",
            'foreground': "#343a40",
            'focuscolor': ''},
        'map': {
            'background': [
                ('active', '#ffffff')],
            'foreground': [
                ('disabled', "#c5c7c7"),
                ('active !disabled', "#4582ec")]}}}

# create and apply custom theme
style.theme_create('myawesometheme', 'clam', theme_settings)
style.theme_use('myawesometheme')

# set the background to white (too lazy to create a frame)
style.master.configure(background="#ffffff")

# add the new widgets that I created
ttk.Radiobutton(text='option 1 - selected', value=1).pack(fill='x', padx=20, pady=(20, 2))
ttk.Radiobutton(text='option 2', value=2).pack(fill='x', padx=20, pady=2)
ttk.Radiobutton(text='option 3', value=3).pack(fill='x', padx=20, pady=2)
ttk.Radiobutton(text='option 4 - disabled', value=4, state='disabled').pack(fill='x', padx=20, pady=(2, 20))

style.master.mainloop()