quick newbie question on variables. please answer

[Toy]

Im a programming newbie, so most of these concepts are basic to me.  I'm
trying to write really basic  CGI programs just to get started.  How
would I pass a text variable that a user entered to find a man page for
a tool?  This is the code I wrote (startx is just a command I wrote in,
but how would I write it so any tool could be inputed) the 3rd line od
code is written wrong for sure:

#!/usr/bin/python
import commands
b = commands.getstatusoutput('man %x!') % startx
print = b

  I know that this is a real basic question, but I am 100% new to
programming and I am self teaching.  Also, are ther large security risks
if this program is on a web server(if so, how could I fix it?)?  Thanks
for your time in advance.