using Python to run other programs

[Frog]

Hi, i'm not a programmer so I have a very stupid question.  I'm trying to 
make a practical script.  I need to run an executable program in it but i 
can't get it to work.  Maybe someone here can figure it out easily:

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#! /python

a = (recipient's e-mail address)

pgp -feat a

(sendmail to address after encryption)
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How do I get python to open the pgp program?

Should I use an environment other than python?

thanks!