There are two problems: one in your code and one in tkinter or Tcl.

The problem with your code is that it creates new Tcl interpreters in loop. Create a single Tcl interpreters and create commands in a loop. This will reduce the leak to constant amount.

The problem with either the tkinter module or the Tcl interpreter is that the reference to created commands should be released when delete the command explicitly (Tcl_DeleteCommand), or create a new command with the same name (Tcl_CreateCommand), or delete the Tcl interpreter (Tcl_DeleteInterp), but for unknown cause this doesn't happen in the last case.