[Python-Dev] PEP needed? Introducing Tcl objects

Martin v. Loewis martin@v.loewis.de
15 Feb 2002 21:13:43 +0100

"Fredrik Lundh" <fredrik@pythonware.com> writes:

> > For backward compatibility, there is an option on the tkapp object to
> > determine whether strings or objects are returned. This is on by
> > default when using Tkinter
> "on" as in "return strings" or "return objects" ?

In Tkinter, it returns objects by default.

> I doubt it's a good idea to change the return type without any
> warning.

This is not as bad as it sounds. For most functions, the return type
does not change at all. Consider

    def winfo_depth(self):
        """Return the number of bits per pixel."""
        return getint(self.tk.call('winfo', 'depth', self._w))

'winfo depth' will return a Tcl int in Tcl, which is currently
converted to a string in _tkinter, then converted back to an int.
With the change, tk.call will already return an int, so the getint
invocation becomes a no-op.

For others, a conversion into string will continue to return the value
that it currently returns:

>>> l=Tkinter.Label()
>>> l.config("foreground")[3]
<color object at 0x0824b4b0>
>>> str(_)

I would expect that few if any applications will be affected; those
would need to change the default after import Tkinter.

> if the default is "use old behaviour", check it in.
> if you insist on changing the return types, post it to SF.

I'd like to change the return types. If that is not acceptable, I'd
like to produce a DeprecationWarning if Tkinter is imported and the
new-style behaviour (return objects) is not enabled.