Question

1. I have a bunch of Python functions. Let’s call them foo, bar and baz. They accept variable number of string arguments and does other sophisticated things (like accessing the network).

2. I want the “user” (let’s assume he is only familiar with Tcl) to write scripts in Tcl using those functions.

Here’s an example (taken from Macports) that user can come up with:

post-configure {
    if {[variant_isset universal]} {
        set conflags ""
        foreach arch ${configure.universal_archs} {
            if {${arch} == "i386"} {append conflags "x86 "} else {
                if {${arch} == "ppc64"} {append conflags "ppc_64 "} else {
                    append conflags ${arch} " "
                }
            }
        }

        set profiles [exec find ${worksrcpath} -name "*.pro"]
        foreach profile ${profiles} {
            reinplace -E "s|^(CONFIG\[ \\t].*)|\\1 ${conflags}|" ${profile}

            # Cures an isolated case
            system "cd ${worksrcpath}/designer && \
                    ${qt_dir}/bin/qmake -spec ${qt_dir}/mkspecs/macx-g++ -macx \
                    -o Makefile python.pro"
        }
    }
}

Here, variant_issset, reinplace are so on (other than Tcl builtins) are implemented as Python functions. if, foreach, set, etc.. are normal Tcl constructs. post-configure is a Python function that accepts, well, a Tcl code block that can later be executed (which in turns would obviously end up calling the above mentioned Python “functions”).

Is this possible to do in Python? If so, how?

from Tkinter import *; root= Tk(); root.tk.eval('puts [array get tcl_platform]') is the only integration I know of, which is obviously very limited (not to mention the fact that it starts up X11 server on mac).

Answer 1

With a little experimentation I discovered you can do something like this to create a tcl interpreter, register a python command, and call it from Tcl:

import Tkinter

# create the tcl interpreter
tcl = Tkinter.Tcl()

# define a python function
def pycommand(*args):
    print "pycommand args:", ", ".join(args)

# register it as a tcl command:
tcl_command_name = "pycommand"
python_function = pycommand
cmd = tcl.createcommand(tcl_command_name, python_function)

# call it, and print the results:
result = tcl.eval("pycommand one two three")
print "tcl result:", result

When I run the above code I get:

$ python2.5 /tmp/example.py
pycommand args: one, two, three
tcl result: None