# Handling LAMMPS errors

Compiling the shared library with [C++ exception support](exceptions)
provides a better error handling experience. Without exceptions the
LAMMPS code will terminate the current Python process with an error
message. C++ exceptions allow capturing them on the C++ side and
rethrowing them on the Python side. This way LAMMPS errors can be
handled through the Python exception handling mechanism.

``` python
from lammps import lammps, MPIAbortException

lmp = lammps()

try:
   # LAMMPS will normally terminate itself and the running process if an error
   # occurs. This would kill the Python interpreter. To avoid this, make sure to
   # compile with LAMMPS_EXCEPTIONS enabled. This ensures the library API calls
   # will not terminate the parent process. Instead, the library wrapper will
   # detect that an error has occured and throw a Python exception

   lmp.command('unknown')
except MPIAbortException as ae:
   # Single MPI process got killed. This would normally be handled by an MPI abort
   pass
except Exception as e:
   # All (MPI) processes have reached this error
   pass
```

:::: warning
::: title
Warning
:::

Capturing a LAMMPS exception in Python can still mean that the current
LAMMPS process is in an illegal state and must be terminated. It is
advised to save your data and terminate the Python instance as quickly
as possible.
::::