Python exceptions in Docker logs marked as stream: stdout

Question

I want parse and handle all errors from docker container, but python exceptions marked as stdout, when I expect stderr.

As example simple app.py

Answer 1

docker logs separating stdout from stderr:

$ docker run -d --name foo busybox ls abcd
9a432862fb838b422d6b06446bc817d71cef09254059ec1ca92d0742580b81a4
$ docker logs foo > stdout.log 2>stderr.log
$ cat stdout.log 
$ cat stderr.log 
ls: abcd: No such file or directory
$

vs

$ docker run -d --name foo busybox ls /
5aff475fe0aa864c22633e7b915f7271e0a009b003371e9cdf2fbf1bae224709
$ docker logs foo > stdout.log 2>stderr.log
$ cat stdout.log 
bin
dev
etc
home
lib
lib64
linuxrc
media
mnt
opt
proc
root
run
sbin
sys
tmp
usr
var
$ cat stderr.log 
$