For C programmers, however, error checking always has to be explicit. All

functions in the Python/C API can raise exceptions, unless an explicit claim is

made otherwise in a function's documentation. In general, when a function

encounters an error, it sets an exception, discards any object references that

it owns, and returns an error indicator --- usually *NULL* or ``-1``. A few

functions return a Boolean true/false result, with false indicating an error.

Very few functions return no explicit error indicator or have an ambiguous

return value, and require explicit testing for errors with

:c:func:`PyErr_Occurred`.