better use of os.system()

[Bob Roberts]

How can I make it so that I can pass anything into os.system() any
command that I would type into the command line (bash on cygwin)?  For
example, "lower" is a small script  of mine that I use frequently, and
I would like to be able to call if from python.  os.system("lower")
results in:
lower: not found

I want it to run "lower" just like it would if I typed "lower" at the
bash prompt.  How can I do that?