[SOLVED] Communicating Python Exception to a shell script

Issue

I have a test.py python script which contains following code.

def f(x):
    if x < 0:
        raise Exception("negative number")

    else: 
        return x

I have written another shell script test.sh that runs the python function inside it. The code is as follows

#!/bin/bash
X=$1

y=$(python3 -c "from test import f; print(f(`echo $X`))")
echo this is y: $y

The shell script works fine when input is positive i.e bash test.sh 1. This gives this is y: 1.

However, when the input is negative i.e bash test.sh -1. It gives a python traceback.

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/home/user/test.py", line 4, in f
    raise Exception("negative number")
Exception: negative number
this is y:

Question: what changes should be made to avoid the above output (avoid printing traceback).

Expected output:

this is y: exception

Solution

Use a try/except that prints exception.

y=$(python3 -c "from test import f
try: print(f(`echo $X`))
except: print('exception')")

Answered By - Barmar

Answer Checked By - Mary Flores (WPSolving Volunteer)