newbie question - executing system commands

[Borzoj]

I'm newbie both in shell scripting and pyhon so please be kind :)
What would be the Python equivalent for following shell code:

for IMAGE_NAME in `ls`; do {
#processing of $IMAGE_NAME
};done


...or in other words what is the easiest way to execute shell
command/external program from python and
get access to it's output?

thx
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