How to pass variables from python script to bash script

Question

I have a bash script, a.sh , and in it I have call a python script b.py . The python script calculates something, and I want it to return a value that will be used later in a.sh . I know I can do

In a.sh:

var=`python b.py`

In b.py:

print x # when x is the value I want to pass

But this is not so convenient, because I also print other messages in b.py

Is there any better way to do it?

Edit:

What I'm doing now is just

var=`python b.py | tail -n 1`

It means I can print many things inside b.py, but only the last line (the last print command, assuming it doesn't contain "\n" in it) will be stored in var.

Thanks for all the answers!

Answer 1

I would print it to a file chosen on the command line then I'd get that value in bash with something like cat.

So you'd go:

python b.py tempfile.txt
var=`cat tempfile.txt`
rm tempfile.txt

[EDIT, another idea based on other answers]

Your other option is to format your output carefully so you can use bash functions like head/tail to pipe only the first/last lines into your next program.