execute_process: how to pass argument to python script

Usage
1 
execute_process(COMMAND ${Python3_EXECUTABLE} my_script.py my_arg)

doesn’t work as intended: my_script.py is executed, but does not see the argument my_arg.

Whereas on the command line

$ python3 my_script.py my_args

does work.

As a minimal example, suppose my_script.py is

import sys
print("my_script found argument", sys.argv[1])
2

This works locally:

% cmake -P run.cmake
-- Found Python3: /usr/bin/python3.9 (found version "3.9.10") found components: Interpreter 
my_script found argument my_arg
% cat my_script.py
import sys
print("my_script found argument", sys.argv[1])
% cat run.cmake
find_package(Python3 REQUIRED COMPONENTS Interpreter)
execute_process(COMMAND ${Python3_EXECUTABLE} my_script.py my_arg)

Can you provide a fuller example that shows the problem?

3

Thank you very much, Ben.

Things didn’t work in my more complex code because I confused upper and lower case in a variable name.

Apologies, Joachim

4

Hello everyone,

I faced issue when send back argument from python to Cmake I used
os.environ[“MY_DATA”] = ‘2’
print(os.environ[“MY_DATA”])

and I read the env variable in Cmake was

set(env $ENV{MY_DATA})
message(“Helloo Python your value is : ${env}”)

It not work , Can someone explain for me why

5

Can you provide the relationship between these two snippets of code? Is the Python script doing the os.environ setting launching CMake somehow? Can you share that?

6

Hi Ben ,

Thanks for reply

For 2 snippet code I wanted trial to send a message from Python to CMake parents , when it call to Python I trial to export an env variable by Python to use in CMake for other purpose. I used with excute_process to call Python script in CMake parents and message to print value Python return back . But it was not work

7

A child process cannot set the environment of the parent process, so a Python script setting its environment has no effect on the CMake process calling it via execute_process.

8

Thanks for your reply Ben .

Are there anyway Python scripts can export env for other scripts use or it just only set its env and other scripts can’t see ? I used to set env variable in CMake and shell. Python scripts use env (export env in shell and set env $ENV{env} in CMake) . I just trial some way to export env variables from Python.

9

The environment can only be modified for the currently running processes and new processes started (via passing them to the execve or CreateProcess family of APIs).