On 12/15/13, 5:06 PM, Chris Angelico wrote:
Yeah, but there's a difference between passing your GUI incantations on to a library function (written in C but now just part of a binary library) and feeding them to a completely different language interpreter. When I write something with PyGTK, I can't, even in theory, give it arbitrary C code to execute. From what I understand here, that *is* true of Tcl, which means that the Python download contains a Python interpreter and a Tcl interpreter. I'm not saying that's a bad thing to do, but it is calculated to provoke remark.
Yes, a Tkinter app has both a Python interpreter and an underlying Tcl interpreter. Let's be clear about that.
The technical reason for this is that, during Python's early development, Tk was the simplest, most powerful and OSS-friendly GUI toolkit out there (compared to, let's say, Motif). Its reliance on Tcl was a plus because Tcl's C API is exceptionally clean and easy to embed/call from other C libraries (that was Tcl's original main focus, embedding in C).
Embedding the Tcl interpreter remains a sound decision today. It makes it trivial to keep Tkinter updated in sync with Tk updates, since the Tcl interpreter does most of the heavy lifting. The recent effort to wrap Tk's new themed widgets is a good one: nearly all of the work was done at the Python level. Compare this approach to Perl's original one, which stripped out Tcl and implemented Tk integration entirely in C. Any updates require heavy lifting in C and, in fact, Perl/Tk has not kept up with Tk's main line of development (it does not run natively on the Mac, for instance).
Calling through Tkinter to Tcl also provides some other conveniences. If you're writing a Tkinter app and want to access some platform-specific functionality that requires C calls, that may require a library extension written against Tcl/Tk's C API (i.e. the Mac's NSServices API--that can't be accessed using ctypes because it hooks into the window server). Fortunately, Tk is very easy to extend in C--much simpler than extending wxWidgets or Qt.
Finally, Tcl is itself a fully-featured, general programming language that is a peer to Python both generationally and in terms of its capabilities; the main way it lags is in the size of its development community. In other words, you are not handing the ball off to a 90-pound weakling if you need to call into Tcl from Python via Tkinter. ;-)
--Kevin -- Kevin Walzer Code by Kevin/Mobile Code by Kevin http://www.codebykevin.com http://www.wtmobilesoftware.com -- https://mail.python.org/mailman/listinfo/python-list
