Python 3.14.7 tkinter fails when per-user installation path contains a space

[saedkh-cell]

Bug report

Bug description:

Bug description

On Windows 10, tkinter cannot initialize when the official Python 3.14.7
installation is located under a user-profile path containing a space.

Python was installed using the official 64-bit installer with the default
per-user installation options. The issue persisted after completely
uninstalling and reinstalling Python.

The Tcl/Tk archives are present:

• tcl\libtcl9.0.4.zip
• tcl\libtk9.0.4.zip

Running the installation normally fails:

$python = "$env:LOCALAPPDATA\Programs\Python\Python314\python.exe"
& $python -m tkinter

The result is:

_tkinter.TclError: Cannot find a usable init.tcl in the following directories:
    <redacted user profile>/AppData/Local/Programs/Python/Python314/lib/tcl9.0
    ...
This probably means that Tcl wasn't installed properly.

However, mapping the exact same Python installation to a drive letter makes
Tkinter work immediately:

subst T: "$env:LOCALAPPDATA\Programs\Python\Python314"
T:\python.exe -m tkinter
subst T: /d

The Tk demonstration window opens successfully through T:\python.exe.

No Python or Tcl/Tk files are copied or changed between the two tests. The only
difference is whether the same installation is accessed through its original
path, which contains a space, or through a drive-letter path without spaces.

A minimal program produces the same result:

import tkinter as tk

root = tk.Tk()
root.destroy()

Expected behavior

tkinter should initialize from the default per-user installation location
even when the Windows account/profile name contains a space.

Actual behavior

tkinter reports that it cannot find a usable init.tcl. Accessing the same
installation through a drive-letter mapping without spaces resolves the
failure.

Reproduction steps

1. Use a Windows account whose user-profile directory contains a space.

2. Install official Python 3.14.7 64-bit using the default per-user options.

3. Run:

   & "$env:LOCALAPPDATA\Programs\Python\Python314\python.exe" -m tkinter

4. Observe the Cannot find a usable init.tcl error.

5. Run:

   subst T: "$env:LOCALAPPDATA\Programs\Python\Python314"
   T:\python.exe -m tkinter
   subst T: /d

6. Observe that Tkinter now starts successfully.

Python version

Python 3.14.7
tags/v3.14.7:823f032
MSC v.1944 64 bit (AMD64)

Operating system

Windows 10 10.0.19045
64-bit

Additional checks

The installed archives exist and are not empty:

libtcl9.0.4.zip    1,121,107 bytes
libtk9.0.4.zip       297,208 bytes

The problem remained after:

• Uninstalling Python 3.14.7
• Reinstalling it with the official installer
• Using the default installation options
• Confirming that the Tcl/Tk component is registered as installed

This appears related to Tcl/Tk 9 ZIP-library discovery or mounting when the
Python installation path contains a space.

Related issues checked

• CPython issue Tkinter - Can't find a usable init.tcl #111754 concerns Tcl library discovery with Python 3.11/3.12
  and a different interpreter/path scenario. It does not reproduce this
  Python 3.14.7 ZIP-mounting failure or the successful subst comparison.
• CPython issue 3.13: cannot run python -m tkinter due to missing init.tcl #126592 concerns a Python 3.13 runtime installed by uv, not
  the official Python 3.14.7 Windows installer.
• Nuitka issue bpo-31754: Fix the PyBuffer Documentation #3993 concerns Nuitka's build plugin detecting the new zipped
  Tcl/Tk layout. In that report, ordinary Python runs Tkinter successfully;
  here, ordinary official CPython itself fails until its path has no spaces.

CPython versions tested on:

3.14

Operating systems tested on:

Windows