I want to create text editor that have coloring feature, Bold,Italic, ... and too many basically Office Program feature for users of my program. but creating this will take too much of my time. so is there a module, package or code for this ?
Thanks.
Gtk3 already has Gtk.TextView and Gtk.TextBuffer which has the requirements you mention (though might be missing some of the more sophisticated ones of a real Office suite). It can also insert images, and do many other tricks. Of course, you have to provide the commands to do steer the widget into executing each of them. 
Another possibility is using a web-based editor, and include webkit in your project.
Python GTK3 Basic Text Editor Like MS Office, LibreOffice