Embedding python code into text document question.

[Thomas Troeger]

Ok I've written a small example program to clarify matters:

================ [SNIP] ================
#!/usr/bin/python

import os, sys, time

def template(src, dst, sep):
         """
         Copy file from src to dst, executing embedded python code.
         """
         try:
                 # read template file.
                 f=open(src, "rU")
                 data="".join(f.readlines())
                 f.close()

                 # find embedded python code and execute it.
                 while True:
                         # find embedded embedded python command.
                         offset=data.find(sep)
                         if offset < 0:
                                 break
                         offset2=data.find(sep, offset+1)
                         if offset2 < 0:
                                 break
                         cmd=data[offset+len(sep):offset2]

                         # execute command.
                         try:
                                 ret=""
                                 exec(compile(cmd,
					'<from string>', 'exec'))
                         except:
                                 print "error compiling code `%s'." % cmd

                         # substitute command with return value.
                         data=data[:offset]+str(ret)+\
				data[offset2+len(sep):]

                 # write translated input.
                 f=open(dst, "w")
                 f.write(data)
                 f.close()
         except:
                 print "error processing template file `%s'." % src

# ------------------------------ main -------------------------------

if len(sys.argv) > 2:
         template(sys.argv[1], sys.argv[2], '$$')
================ [SNIP] ================

This is the example input that works:

================ [SNIP] ================
process id: $$ret=os.getpid()$$
current date: $$ret=time.ctime()$$
superuser: $$
if os.geteuid():
     ret="No"
else:
     ret="Yes"$$
================ [SNIP] ================

Now the `ret= ...' mechanism is not nice, I'd prefer to have a return 
statement instead.