EditorWindow.py has this function, applied to editor and shell windows, which is obsolete for Python3 and unicode identifiers.

def fixwordbreaks(root):
    # Make sure that Tk's double-click and next/previous word
    # operations use our definition of a word (i.e. an identifier)
    tk = root.tk
    tk.call('tcl_wordBreakAfter', 'a b', 0) # make sure word.tcl is loaded
    tk.call('set', 'tcl_wordchars', '[a-zA-Z0-9_]')
    tk.call('set', 'tcl_nonwordchars', '[^a-zA-Z0-9_]')

Double clicking selects a contiguous sequence of 'word' or 
'nonword' characters.
"Control-backspace deletes word left, Control-DEL deletes word right."
"Control-left/right Arrow moves by words in a strange but useful way."

It might be more useful if the REs were expanded.