from subprocess import Popen, PIPE
p1 = Popen(["foo"], stdout=PIPE)
p2 = Popen(["bar"], stdin=p1.stdout, stdout=PIPE)
p1.stdout.close() # Allow p1 to receive a SIGPIPE if p2 exits.
output, _ = p2.communicate()
When you're not writing shell, just use the tools the language gives you.
For the matter, I think a shell script is cleaner than a python script for devops; but I don't think the composability of unix tools is that much of an advantage compared to the amount of python libraries out there.
I'm likely to be using Python programs and other programs in those shell scripts. The beauty of shell is that it makes it so easy to compose programs written in different languages.
I think the advantages of using a single language for everything outweigh the disadvantages - see e.g. http://www.teamten.com/lawrence/writings/java-for-everything... (though actually my single language is Scala)
I'm curious because these simple things that are delightfully easy in bash often turn out to be surprisingly tedious in other languages.
Of course, some things are tedious in bash too. But a basic principle of shell scripting is that you call other programs to do the stuff you don't want to do in shell.
I agree it is tedious, but to be honest, reading and writing to stdin/out isn't something that would commonly need to be done in a robust system. If the world were perfect you would use library functions.
I definitely think there is scope for a language that works well as an interactive shell, and as a general purpose language. They have somewhat conflicting constraints but I'm sure we can do better than Bash. Have you seen how [ is implemented?