python calling python

[Larry Whitley]

I think the light is begining to dawn...

I'm using main() in both myProgram1 and myProgram2 as the starting points
for the programs. And, myProgram2 has an "from myProgram1 import spam" in it
to get the useful function from myProgram1.  It never entered my mind that
myProgram1.main() would be run when myProgram2 said import.  In addition to
this I have coded "main()" as "free code" so kick things off.

I might as well air my dirty laundry.  Perhaps I'll learn what else I'm
doing wrong.  The general form of my python files is this:

# start of file --------------------------

import various things

class A:
    def function in class

class B:
    def function in class

def function called below

def function called below

def main()
    parses sys.argv to get arguments

main() # to get main called

# end of file ---------------------------

Anything else in the above considered harmful in Python?

Larry


"Alex Martelli" <alex at magenta.com> wrote in message
news:8nu8ea09uh at news2.newsguy.com...
> "Larry Whitley" <ldw at us.ibm.com> wrote in message
> news:8nu4i7$14hu$1 at news.rchland.ibm.com...
> > I'm sure the answer to this is straightforward, but I can't find it in
the
> > documentation.
> >
> > How does one call python from python?  For example:  If the main() in
> > myProgram1.py wants to call the main() in myProgram2.py with parameters,
> > what incantation should it use?
>
> I'm not quite sure what you mean.  If, by 'main()', you mean an
> actual function thus called, then it will be something like:
>
> -- myProgram1.py:
>
> def main(some,parms):
>     import myProgram2
>     myProgram2.main('other','parameters')
>
> -- myProgram2.py:
>
> def main(someother, args):
>     print someother, args
>
> -- end
>
> but, from what you say below, it doesn't seem that it's about this...:
>
>
> > I'm trying to use ...
> >
> > os.system( "python /myPath/myProgram2.py -myparm1 xxx -myparm2 yyy" )
> >
> > ...from myProgram1 but it doesn't seem to work.  (It appears to re-enter
> > main() in myProgram1 with myProgram2's parms).
>
> This should run a completely different process and I don't see how
> myProgram1.py's "main" could be re-entered, whatever exactly you mean
> by this.
>
> Anyway, the code that runs when you do "python pip.py" is the "free"
> code that does not belong to any function or class; this code is also
> run when you "import pip" from another Python program.  Sometimes,
> one protects part of such code (and makes it easily executable from
> the outside as above) with the idiom:
>
> def main():
>     pass
>     # whatever you'd otherwise have as 'free code'...
>
> if __name__=='__main__':
>     main()
>
> The 'if' is only satisfied if this is run directly from Python rather
> than imported from another Python program.  But if you've used this
> idiom, then import-then-call is the best way to run from the outside.
>
> Program arguments are placed in the list sys.argv.  Just import sys,
> save the sys.argv in some local variable if you will require it again,
> then set it to whatever you want it to be for the purpose of calling
> the other program, before you do the import-and-call-main thing.
>
>
> Alex
>
>
>