Detecting sys.exit() and ValueError from a python script in bash script

I created a bash script that manages multiple related python scripts based on specific conditions (i.e., run this script while file has < x number of lines, run a different script if..., etc.). I am using entry points to execute these python scripts within the bash script.

When validating the bash script I found some edge cases where all the conditions fail, resulting in a sys.exit(load_entry_point('Program', 'console_scripts', 'iter')()) and ValueError: Nothing was generated (designated within the python program to be raised if nothing happens).

After looking on SO, I tried something like this within some of my conditionals:

    if [ $? -ne 0 ];
    then
        echo "exit 1"
    fi
    echo "EXIT 0"

I continue to get EXIT 0, suggesting no errors are being detected. What I am not understanding here?

For clarity, my goal is to detect any errors thrown by the invoked python scripts to have the bash script respond accordingly.

Here is an idea of what the bash script is like:

Iter=1
while [ $nr_lines -lt 17 ]; do

    if [ $Iter -eq 5 ]; then

        echo ''
        echo 'Relax parameter. Iteration:' $Iter

        relax -i $Iter -o ./dir

        nr_lines=$(wc -l < ./dir/output$Iter.csv)
        
        let Iter++

    else

        echo ''
        echo 'Iteration:' $Iter

        iter -i $Iter -o ./dir

        nr_lines=$(wc -l < ./dir/output$Iter.csv)
        
        let Iter++
    fi
done

I have tried putting the conditional for error capturing here:

Iter=1
while [ $nr_lines -lt 17 ]; do

    if [ $Iter -eq 5 ]; then

        echo ''
        echo 'Relax parameter. Iteration:' $Iter

        relax -i $Iter -o ./dir

        nr_lines=$(wc -l < ./dir/output$Iter.csv)
        
        let Iter++

    else

        echo ''
        echo 'Iteration:' $Iter

        iter -i $Iter -o ./dir

        nr_lines=$(wc -l < ./dir/output$Iter.csv)
        
        let Iter++
    fi

    if [ $? -ne 0 ];
    then
        echo "exit 1"
    fi
    echo "EXIT 0"

done

and here:

Iter=1
while [ $nr_lines -lt 17 ]; do

    if [ $Iter -eq 5 ]; then

        echo ''
        echo 'Relax parameter. Iteration:' $Iter

        relax -i $Iter -o ./dir

        nr_lines=$(wc -l < ./dir/output$Iter.csv)
        
        let Iter++

    else

        echo ''
        echo 'Iteration:' $Iter

        iter -i $Iter -o ./dir

        nr_lines=$(wc -l < ./dir/output$Iter.csv)
        
        let Iter++
    fi

done

if [ $? -ne 0 ];
then
    echo "exit 1"
fi
echo "EXIT 0"

and both return EXIT 0, suggesting no errors have occurred.

Change

        iter -i $Iter -o ./dir

to

        if ! iter -i $Iter -o ./dir
        then
            echo "iter failed"
            break
        fi

This directly tests the exit status of the python script run by iter. If it exits with a non-zero status, you print the message and break out of the while loop.

You can do similarly with relax.