Python, pipes, and the "-c" option in the command line

Question

I vaguely recall being able to do something like this in Python:

cat foo | python -c "<some python code>" | grep blah | ... 

For some reason I'm blanking on how to actually use this to run Python code on each line of the input file. For instance, say I wanted to change every instance of the word "apple" in the original file to "orange"; how would I do that?

Answer 1

I don't see how this can be helpful more than once, but here's a one-liner:

cat file | grep apple | python -c "for line in __import__('sys').stdin: print line.replace(\"apple\", \"orange\"),"