# Interfacing with external code

Some neural simulations benefit from a direct connections to external libraries, e.g. to support real-time input from a sensor (but note that Brian currently does not offer facilities to assure real-time processing) or to perform complex calculations during a simulation run.

If the external library is written in Python (or is a library with Python bindings), then the connection can be made either using the mechanism for User-provided functions, or using a network operation.

In case of C/C++ libraries, only the User-provided functions mechanism can be used. On the other hand, such simulations can use the same user-provided C++ code to run with the Standalone code generation mode. In addition to that code, one generally needs to include additional header files and use compiler/linker options to interface with the external code. For this, several preferences can be used that will be taken into account for `cython` and the `cpp_standalone` device. These preferences are mostly equivalent to the respective keyword arguments for Python’s `distutils.core.Extension` class, see the documentation of the `cpp_prefs` module for more details.