Calling a Python function from a shell script

Question

I am trying to figure out how to call a Python function from a shell script.

I have a Python file with multiple functions and I need to use the values returned by them in my shell script. Is there a way to do it.

I am doing this in order to read a config file using Python and getting the values in shell. Is there any other better way to achieve this.

test.py contains:

import ConfigParser

config = ConfigParser.ConfigParser()
config.read("test.conf")

def get_foo():
    return config.get("locations", "foo")

def get_bar():
    return config.get("locations", "bar")

I need to store the values returned by the Python functions in a shell variable.

Answer 1

You can send the result of your functions to the standard output by asking the Python interpreter to print the result:

python -c 'import test; print test.get_foo()'

The -c option simply asks Python to execute some Python commands.

In order to store the result in a variable, you can therefore do:

RESULT_FOO=`python -c 'import test; print test.get_foo()'`

or, equivalently

RESULT=$(python -c 'import test; print test.get_foo()')

since backticks and $(…) evaluate a command and replace it by its output.

PS: Getting the result of each function requires parsing the configuration file each time, with this approach. This can be optimized by returning all the results in one go, with something like:

ALL_RESULTS=$(python -c 'import test; print test.get_foo(), test.get_bar()')

The results can then be split and put in different variables with

RESULT_BAR=$(echo $ALL_RESULTS | cut -d' ' -f2)

which takes the second result and puts it in RESULT_BAR for example (and similarly: -fn for result #n).

PPS: As Pablo Maurin mentioned, it would probably be easier to do everything in a single interpreter (Python, but maybe also the shell), if possible, instead of calculating variables in one program and using them in another one.