'Unmatched open brace' error when adding item to ttk.Treeview
python, tkinter, treeview
Solution
At it's core, Tkinter is a wrapper around a Tcl interpreter. To Tcl, curly braces are special unless they are escaped. Curly braces are the most common way to create a Tcl list. If you see `unmatched open brace in list`, that's a Tcl error related to the fact that you have unbalanced braces.
This looks like a Tkinter bug to me -- the tkinter wrapper is incorrectly quoting data before passing it on to the Tcl interpreter. When you place a backslash in front of the curly brace, this now becomes a valid Tcl string, which is why you no longer see the error.
This has been reported on the python bug tracker as issue #15861
Problem
I'm attempting to add an item to a `ttk.Treeview` instance in my Python script that builds a basic UI. The insertion code looks like this: ``` tree.insert(my_id, 'end', todo_id, text="Line " + str(line_num), values=(str(todo_text), owner), # I have 2 cols, 'text' and 'owner' tags=['#todo_entry']) ``` I'm finding that when setting the string `todo_text` in the column named 'text', Tkinter throws an error when it encounters a particular string: _tkinter.TclError: unmatched open brace in list and the only thing I can think of as the reason for this, is that the string in question contains a curly brace. Here is the string it broke on: `'// static class Properties { // TODO, temp class'` This seems to happen whether or not I use `todo_text` or `str(todo_text)`. Is the text string being parsed somehow? What am I missing?