Ultimately, this C file is an extension module for Python, not a standalone C program
that embeds Python (though C could just as well be on top). To compile it into a
dynamically loaded module file, run the makefile in Example 20-31 on Cygwin (and
use something similar on other platforms). As we learned earlier in this chapter, the
resulting cregister.dll file will be loaded when first imported by a Python script if it is
placed in a directory on Python’s module search path (e.g., in. or PYTHONPATH settings).

Example 20-31. PP4E\Integrate\Embed\Regist\makefile.regist

######################################################################

Cygwin makefile that builds cregister.dll. a dynamically loaded

C extension module (shareable), which is imported by register.py

######################################################################

PYLIB = /usr/local/bin
PYINC = /usr/local/include/python3.1

CMODS = cregister.dll

all: $(CMODS)

cregister.dll: cregister.c
gcc cregister.c -g -I$(PYINC) -shared -L$(PYLIB) -lpython3.1 -o $@

clean:
rm -f *.pyc $(CMODS)

Now that we have a C extension module set to register and dispatch Python handlers,
all we need are some Python handlers. The Python module shown in Example 20-32
defines two callback handler functions and imports the C extension module to register
handlers and trigger events.

Example 20-32. PP4E\Integrate\Embed\Regist\register.py

"""
#########################################################################
in Python, register for and handle event callbacks from the C language;
compile and link the C code, and launch this with 'python register.py'
#########################################################################
"""

####################################

C calls these Python functions;

handle an event, return a result

####################################

def callback1(label, count):
return 'callback1 => %s number %i' % (label, count)

def callback2(label, count):
return 'callback2 => ' + label * count

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