Fail to execute multiple commands with apptainer exec

Question

I follow the answers here How to run 2 commands with docker exec to run 2 commands with apptainer exec:

apptainer exec myPython/ bash -c 'activate virtual environment; mpiexec -n 2 python3 main.py'

But I got the following error messages:

[mpiexec@acn93] HYDU_create_process (lib/utils/launch.c:73): execvp error on file srun (No such file or directory)

Any helps are greatly appreciated.