container restart reason OOMKilled with exit code 1

Question

Recently, the same container of several pods in a deployment restarted with OOMKilled event. Here is the description of one of the containers:

State:          Running
      Started:      Tue, 15 Feb 2022 23:33:06 +0000
    Last State:     Terminated
      Reason:       OOMKilled
      Exit Code:    1
      Started:      Fri, 11 Feb 2022 17:48:21 +0000
      Finished:     Tue, 15 Feb 2022 23:33:05 +0000
    Ready:          True
    Restart Count:  1
    Limits:
      cpu:     1
      memory:  512Mi
    Requests:
      cpu:      1
      memory:   512Mi

If the container would exceed the limit of the available memory then it would exit with code 137. And I guess the container did not reached the limit. So my question what could happen if the exit code is 1 and the Reason is OOMKilled.

Update: The process is actually a python app which has threads, this is the code:

ret = subprocess.run(args, stderr=subprocess.PIPE, universal_newlines=True, check=False)
if ret.returncode != 0:
    logging.warning("Executing cmd failed: %s, code: %d, stderr: %s", cmd, ret.returncode, ret.stderr)
    raise Exception("Failed")

and the relevant logs when called, it return with -9:

2022-02-15T23:33:30.510Z WARNING "MainThread - Executing cmd failed: iptables-restore -n -w 3 restore-filter, code: -9, stderr: "
raise Exception("Failed")
Exception: Failed

from the description of subprocess.run(): A negative value -N indicates that the child was terminated by signal N (POSIX only).

So because the exception is raised the python code exited with 1? Probably..