boost.python/RuntimeErrors¶

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boost.python tries hard to provide best possible run-time errors. But often enough they need futher explanation. Some of them are mentioned below:

TypeError: bad argument type for built-in operation¶

Usualy means BPL couldn’t find c++ method/function with appropriate signature. Very often that is wrong number of arguments, wrong argument(s) type and so on.

TypeError: No to_python converter found for C++ type: <type>¶

TypeError: No to_python (by-value) converter found for C++ type: <type>¶

BPL was unable to get C++ value from Python object.

For example, when calling extract<int>(<object>.attr("__len__")()) to get object length you omitted “()”.

RuntimeError: This class cannot be instantiated from Python¶

Attempt to instantiate a class with no_init descriptor. It may be private constructor or abstract class.

RuntimeError: unidentifiable C++ Exception¶

Boost.Python provides a default exception handler that translates selected standard exceptions, then gives up with that message.

To install your own exception translator don’t see tutorial. “) (& missed in register_exception_translator call)
Use that:

struct PodBayDoorException;
void translator(const PodBayDoorException& x) {
  PyErr_SetString(PyExc_UserWarning, "I'm sorry Dave...");
}
BOOST_PYTHON_MODULE(kubrick) {
  register_exception_translator<
  PodBayDoorException>(&translator);
  ...
}