Return a value from python script to the a makefile variable

Question

I have a requirement where I have to run a python script through a makefile. Python script performs some calculations and return a value. I want to get that value in that makefile variable. How I can do that?

I want something like this:

mymakefile.mke

$output = python process.py

process.py

import os

def main():
    value = "01.00.00"
    return value
if __name__ == "__main__":
    main()

Answer 1

If you want the value in a Make variable, you can do this:

output := $(shell python process.py)

(Note the use of := rather than = , because if you use = , Make will run the script every time it evaluates the variable.)

If you want the value in a shell variable within a recipe, look at the syntax you would use on the command line in your shell, which is probably something like:

output=$(python process.py); echo $output

but in a makefile rule you must escape the dollar signs with more dollar signs:

some_target:
    output=$$(python process.py); echo $$output

Note that since each line of a recipe executes in its own sub-shell, the assignment and use of the variable must be on the same line; it won't survive to the next line.