Introduced in#16545
Affects Python 3.7+ on Windows only

TheFromObj function in_tkinter.c attempt to convert aTcl_Obj to an equivalent Python object if possible, and otherwise returns a_tkinter.Tcl_Obj with thetypename attribute set to the original object's type.

However, on Windows, accessing the resulting object's string representationcallsTcl_GetUnicodeFromObj, which converts theTcl_Obj to aString. This side effect isn't mentioned in the Tcl documentation, but isin the Tcl source code. As a result, retrieving the same tk property afterwards will return a Python string instead.

Minimal example:

importtkinterastkroot=tk.Tk()print(type(root.cget("padx")))_=str(root.cget("padx"))# should really not cause any side effectsprint(type(root.cget("padx")))# Windows:# <class '_tkinter.Tcl_Obj'># <class 'str'># Other platforms:# <class '_tkinter.Tcl_Obj'># <class '_tkinter.Tcl_Obj'>

Possible solutions:unicodeFromTclObj should copy the object before passing callingTcl_GetUnicodeFromObj, or handle Unicode without it like on other platforms.

Linked PRs

• gh-101830: Fix Tcl_Obj to string conversion #120884
• [3.13] gh-101830: Fix Tcl_Obj to string conversion (GH-120884) #120905
• [3.12] gh-101830: Fix Tcl_Obj to string conversion (GH-120884) #120913