["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.