How to break a bash for loop from inside a python script?-CodePudding

I have a for loop that runs a python script iteratively. There is a condition inside the python script that, if met, makes unnecessary to keep running the python script or even the for loop. For example:

#Bash Script
for i in {1..15}; do
    echo "Pre Outside ${i}"
    python minimal_test.py $i
    echo "Post Outside ${i}"
done

#Python script
import sys
import subprocess
k = int(sys.argv[1])
end_bash = False

if k == 7:
    end_bash = True
print("Inside "   str(k))
if end_bash:
    bashCommand = "break"
    process = subprocess.Popen(bashCommand, stdout=subprocess.PIPE)

When the loop i in the bash script == 6 and then 7, the program should print:

PreOutside 6
PreInside 6
PostOutside 6    
Pre Outside 7
Pre Inside 7 #The program must end here

However, I get the following error and the program keeps running

File "/software/software/Python/3.9.5-GCCcore-10.3.0/lib/python3.9/subprocess.py", line 1821, in _execute_child
raise child_exception_type(errno_num, err_msg, err_filename)
FileNotFoundError: [Errno 2] No such file or directory: 'break'

Is there a way to tell bash to end the for loop from inside the python script?

CodePudding user response：

Make your Python script exit with an error. Then the shell script becomes

for i in {1..15}; do
    python minimal_test.py "$i" || break
done

In so many words, your Python script should sys.exit(1) to signal an error to the shell (or any calling utility really). The precise number is up to you; any non-zero number is a failure code. (The range is 0-255, i.e. an unsigned char.)

Running break in a subprocess makes no sense; you were starting a new Bash instance which is independent from the one which is running the loop, one in which of course break doesn't do anything useful, and in fact is just a syntax error in isolation.