docker run <IMAGE> <MULTIPLE COMMANDS>

You can do this a couple of ways:

1. Use the -w option to change the working directory:

   -w, --workdir="" Working directory inside the container

   https://docs.docker.com/engine/reference/commandline/run/#set-working-directory--w

2. Pass the entire argument to /bin/bash:

   docker run image /bin/bash -c "cd /path/to/somewhere; python a.py"
   

To run multiple commands in docker, use /bin/bash -c and semicolon ;

docker run image_name /bin/bash -c "cd /path/to/somewhere; python a.py"

In case we need command2 (python) will be executed if and only if command1 (cd) returned zero (no error) exit status, use && instead of ;

docker run image_name /bin/bash -c "cd /path/to/somewhere && python a.py"