annotate PyTypeConversions.cpp @ 71:40a01bb24209 vampyhost

Pull apart some type conversion classes for possible use in VamPy Host

/* -*- c-basic-offset: 8 indent-tabs-mode: t -*- */
/*

 * Vampy : This plugin is a wrapper around the Vamp plugin API.
 * It allows for writing Vamp plugins in Python.

 * Centre for Digital Music, Queen Mary University of London.
 * Copyright (C) 2008-2009 Gyorgy Fazekas, QMUL. (See Vamp sources 
 * for licence information.)

*/

#include <Python.h>

#include "PyTypeConversions.h"

#include <math.h>
#include <float.h>
#include <limits.h>
#ifndef SIZE_T_MAX
#define SIZE_T_MAX ((size_t) -1)
#endif

using std::string;
using std::vector;
using std::cerr;
using std::endl;

/*  Note: NO FUNCTION IN THIS CLASS SHOULD ALTER REFERENCE COUNTS
	(EXCEPT FOR TEMPORARY PYTHON OBJECTS)! */

PyTypeConversions::PyTypeConversions() : 
	m_strict(false),
	m_error(false),
	m_numpyInstalled(false),
	error(m_error) // const public reference for easy access
{
}

PyTypeConversions::~PyTypeConversions()
{
}

/// floating point numbers (TODO: check numpy.float128)
float 
PyTypeConversions::PyValue_To_Float(PyObject* pyValue) const
{
	// convert float
	if (pyValue && PyFloat_Check(pyValue)) 
		//TODO: check for limits here (same on most systems)
		return (float) PyFloat_AS_DOUBLE(pyValue);
	
	if (pyValue == NULL)
	{
		setValueError("Error while converting object " + PyValue_Get_TypeName(pyValue) + " to float. ",m_strict);
		return 0.0;		
	}
		
	// in strict mode we will not try harder
	if (m_strict) {
		setValueError("Strict conversion error: object" + PyValue_Get_TypeName(pyValue) +" is not float.",m_strict);
		return 0.0;
	}

	// convert other objects supporting the number protocol
	if (PyNumber_Check(pyValue))
	{
		PyObject* pyFloat = PyNumber_Float(pyValue); // new ref
		if (!pyFloat)
		{
			if (PyErr_Occurred()) {PyErr_Print(); PyErr_Clear();}
			setValueError("Error while converting " + PyValue_Get_TypeName(pyValue) + " object to float.",m_strict);
			return 0.0;
		}
		float rValue = (float) PyFloat_AS_DOUBLE(pyFloat);
		Py_DECREF(pyFloat);
		return rValue;
	}
/*	
	// convert other objects supporting the number protocol
	if (PyNumber_Check(pyValue)) 
	{	
		// PEP353: Py_ssize_t is size_t but signed !
		// This will work up to numpy.float64
		Py_ssize_t rValue = PyNumber_AsSsize_t(pyValue,NULL);
		if (PyErr_Occurred()) 
		{
			PyErr_Print(); PyErr_Clear();
			setValueError("Error while converting integer object.",m_strict);
			return 0.0;
		}
		if (rValue > (Py_ssize_t)FLT_MAX || rValue < (Py_ssize_t)FLT_MIN)
		{
			setValueError("Overflow error. Object can not be converted to float.",m_strict);
			return 0.0;
		}
		return (float) rValue;
	}
*/	
    // convert string
	if (PyString_Check(pyValue))
	{
		PyObject* pyFloat = PyFloat_FromString(pyValue,NULL);
		if (!pyFloat) 
		{
			if (PyErr_Occurred()) { PyErr_Print(); PyErr_Clear(); }
			setValueError("String value can not be converted to float.",m_strict);
			return 0.0;
		}
		float rValue = (float) PyFloat_AS_DOUBLE(pyFloat);
		if (PyErr_Occurred()) 
		{
			PyErr_Print(); PyErr_Clear(); 
			Py_CLEAR(pyFloat);
			setValueError("Error while converting float object.",m_strict);
			return 0.0;
		}
		Py_DECREF(pyFloat);
		return rValue;
	}
	
	// convert the first element of any iterable sequence (for convenience and backwards compatibility)
	if (PySequence_Check(pyValue) && PySequence_Size(pyValue) > 0) 
	{
		PyObject* item = PySequence_GetItem(pyValue,0);
		if (item)
		{
			float rValue = this->PyValue_To_Float(item);
			if (!m_error) {
				Py_DECREF(item);
				return rValue;
			} else {
				Py_CLEAR(item);
				std::string msg = "Could not convert sequence element to float. ";
				setValueError(msg,m_strict);
				return 0.0;
			}
		}
	}

    // give up
	if (PyErr_Occurred()) { PyErr_Print(); PyErr_Clear(); }
	std::string msg = "Conversion from " + PyValue_Get_TypeName(pyValue) + " to float is not possible.";
	setValueError(msg,m_strict);
#ifdef _DEBUG
	cerr << "PyTypeConversions::PyValue_To_Float failed. " << msg << endl;
#endif	
	return 0.0;
}

/// size_t (unsigned integer types)
size_t 
PyTypeConversions::PyValue_To_Size_t(PyObject* pyValue) const
{
	// convert objects supporting the number protocol 
	if (PyNumber_Check(pyValue)) 
	{	
		if (m_strict && !PyInt_Check(pyValue) && !PyLong_Check(pyValue)) 
			setValueError("Strict conversion error: object is not integer type.",m_strict);
		// Note: this function handles Bool,Int,Long,Float
		// speed is not critical in the use of this type by Vamp
		// PEP353: Py_ssize_t is size_t but signed ! 
		Py_ssize_t rValue = PyInt_AsSsize_t(pyValue);
		if (PyErr_Occurred()) 
		{
			PyErr_Print(); PyErr_Clear();
			setValueError("Error while converting integer object.",m_strict);
			return 0;
		}
		// this test is nonsense -- neither part can occur
		// owing to range of data types -- size_t is at least
		// as big as long, and unsigned is always non-negative
/*
		if ((unsigned long)rValue > SIZE_T_MAX || (unsigned long)rValue < 0)
		{
			setValueError("Overflow error. Object can not be converted to size_t.",m_strict);
			return 0;
		}
*/
		return (size_t) rValue;
	}
	
	// in strict mode we will not try harder and throw an exception
	// then the caller should decide what to do with it
	if (m_strict) {
		setValueError("Strict conversion error: object is not integer.",m_strict);
		return 0;
	}
	
	// convert string
	if (PyString_Check(pyValue))
	{
		PyObject* pyLong = PyNumber_Long(pyValue);
		if (!pyLong) 
		{
			if (PyErr_Occurred()) { PyErr_Print(); PyErr_Clear(); }
			setValueError("String object can not be converted to size_t.",m_strict);
			return 0;
		}
		size_t rValue = this->PyValue_To_Size_t(pyLong);
		if (!m_error) {
			Py_DECREF(pyLong);
			return rValue;
		} else {
			Py_CLEAR(pyLong);
			setValueError ("Error converting string to size_t.",m_strict);
			return 0;
		}
	}
	
	// convert the first element of iterable sequences
	if (PySequence_Check(pyValue) && PySequence_Size(pyValue) > 0) 
	{
		PyObject* item = PySequence_GetItem(pyValue,0);
		if (item)
		{
			size_t rValue = this->PyValue_To_Size_t(item);
			if (!m_error) {
				Py_DECREF(item);
				return rValue;
			} else {
				Py_CLEAR(item);
				setValueError("Could not convert sequence element to size_t. ",m_strict);
				return 0;
			}
		}
	}
	
    // give up
	if (PyErr_Occurred()) { PyErr_Print(); PyErr_Clear(); }
	std::string msg = "Conversion from " + this->PyValue_Get_TypeName(pyValue) + " to size_t is not possible.";
	setValueError(msg,m_strict);
#ifdef _DEBUG
	cerr << "PyTypeConversions::PyValue_To_Size_t failed. " << msg << endl;
#endif	
	return 0;
}

/// long and int
long 
PyTypeConversions::PyValue_To_Long(PyObject* pyValue) const
{
	// most common case: convert int (faster)
	if (pyValue && PyInt_Check(pyValue)) {
		// if the object is not NULL and verified, this macro just extracts the value.
		return PyInt_AS_LONG(pyValue);
	} 
	
	// long
	if (PyLong_Check(pyValue)) {
		long rValue = PyLong_AsLong(pyValue);
		if (PyErr_Occurred()) { 
			PyErr_Print(); PyErr_Clear(); 
			setValueError("Error while converting long object.",m_strict);
			return 0;
		}
		return rValue;
	}
	
	if (m_strict) {
		setValueError("Strict conversion error: object is not integer or long integer.",m_strict);
		return 0;
	}
	
	// convert all objects supporting the number protocol
	if (PyNumber_Check(pyValue)) 
	{	
		// Note: this function handles Bool,Int,Long,Float
		// PEP353: Py_ssize_t is size_t but signed ! 
		Py_ssize_t rValue = PyInt_AsSsize_t(pyValue);
		if (PyErr_Occurred()) 
		{
			PyErr_Print(); PyErr_Clear();
			setValueError("Error while converting integer object.",m_strict);
			return 0;
		}
		if (rValue > LONG_MAX || rValue < LONG_MIN)
		{
			setValueError("Overflow error. Object can not be converted to size_t.",m_strict);
			return 0;
		}
		return (long) rValue;
	}
	
	// convert string
	if (PyString_Check(pyValue))
	{
		PyObject* pyLong = PyNumber_Long(pyValue);
		if (!pyLong) 
		{
			if (PyErr_Occurred()) { PyErr_Print(); PyErr_Clear(); }
			setValueError("String object can not be converted to long.",m_strict);
			return 0;
		}
		long rValue = this->PyValue_To_Long(pyLong);
		if (!m_error) {
			Py_DECREF(pyLong);
			return rValue;
		} else {
			Py_CLEAR(pyLong);
			setValueError ("Error converting string to long.",m_strict);
			return 0;
		}
	}
	
	// convert the first element of iterable sequences
	if (PySequence_Check(pyValue) && PySequence_Size(pyValue) > 0) 
	{
		PyObject* item = PySequence_GetItem(pyValue,0);
		if (item)
		{
			size_t rValue = this->PyValue_To_Long(item);
			if (!m_error) {
				Py_DECREF(item);
				return rValue;
			} else {
				Py_CLEAR(item);
				setValueError("Could not convert sequence element to long. ",m_strict);
				return 0;
			}
		}
	}
	
    // give up
	if (PyErr_Occurred()) { PyErr_Print(); PyErr_Clear(); }
	std::string msg = "Conversion from " + this->PyValue_Get_TypeName(pyValue) + " to long is not possible.";
	setValueError(msg,m_strict);
#ifdef _DEBUG
	cerr << "PyTypeConversions::PyValue_To_Long failed. " << msg << endl;
#endif	
	return 0;
}


bool 
PyTypeConversions::PyValue_To_Bool(PyObject* pyValue) const
{
	// convert objects supporting the number protocol
	// Note: PyBool is a subclass of PyInt
	if (PyNumber_Check(pyValue)) 
	{	
		if (m_strict && !PyBool_Check(pyValue)) 
			setValueError
			("Strict conversion error: object is not boolean type.",m_strict);

		// Note: this function handles Bool,Int,Long,Float
		Py_ssize_t rValue = PyInt_AsSsize_t(pyValue);
		if (PyErr_Occurred()) 
		{
			PyErr_Print(); PyErr_Clear();
			setValueError ("Error while converting boolean object.",m_strict);
		}
		if (rValue != 1 && rValue != 0)
		{
			setValueError ("Overflow error. Object can not be converted to boolean.",m_strict);
		}
		return (bool) rValue;
	}
	
	if (m_strict) {
		setValueError ("Strict conversion error: object is not numerical type.",m_strict);
		return false;
	}
	
	// convert iterables: the rule is the same as in the interpreter:
	// empty sequence evaluates to False, anything else is True
	if (PySequence_Check(pyValue)) 
	{
		return PySequence_Size(pyValue)?true:false;
	}
	
    // give up
	if (PyErr_Occurred()) { PyErr_Print(); PyErr_Clear(); }
	std::string msg = "Conversion from " + this->PyValue_Get_TypeName(pyValue) + " to boolean is not possible.";
	setValueError(msg,m_strict);
#ifdef _DEBUG
	cerr << "PyTypeConversions::PyValue_To_Bool failed. " << msg << endl;
#endif	
	return false;
}

/// string and objects that support .__str__() 
/// TODO: check unicode objects
std::string 
PyTypeConversions::PyValue_To_String(PyObject* pyValue) const
{
	// convert string
	if (PyString_Check(pyValue)) 
	{	
		char *cstr = PyString_AS_STRING(pyValue);
		if (!cstr) 
		{
			if (PyErr_Occurred()) {PyErr_Print(); PyErr_Clear();}
			setValueError("Error while converting string object.",m_strict);
			return std::string();
		}
		return std::string(cstr);
	}
	// TODO: deal with unicode here (argh!)
	
	// in strict mode we will not try harder
	if (m_strict) {
		setValueError("Strict conversion error: object is not string.",m_strict);
		return std::string();
	}
	
	// accept None as empty string
	if (pyValue == Py_None) return std::string();
			
	// convert list or tuple: empties are turned into empty strings conventionally
	if (PyList_Check(pyValue) || PyTuple_Check(pyValue)) 
	{
		if (!PySequence_Size(pyValue)) return std::string();
		PyObject* item = PySequence_GetItem(pyValue,0);
		if (item)
		{
			std::string rValue = this->PyValue_To_String(item);
			if (!m_error) {
				Py_DECREF(item);
				return rValue;
			} else {
				Py_CLEAR(item);
				setValueError("Could not convert sequence element to string.",m_strict);
				return std::string();
			}
		}
	}

	// convert any other object that has .__str__() or .__repr__()
	PyObject* pyString = PyObject_Str(pyValue);
	if (pyString && !PyErr_Occurred())
	{
		std::string rValue = this->PyValue_To_String(pyString);
		if (!m_error) {
			Py_DECREF(pyString);
			return rValue;
		} else {
			Py_CLEAR(pyString);
			std::string msg = "Object " + this->PyValue_Get_TypeName(pyValue) +" can not be represented as string. ";
			setValueError (msg,m_strict);
			return std::string();
		}
	}

	// give up
	PyErr_Print(); PyErr_Clear();
	std::string msg = "Conversion from " + this->PyValue_Get_TypeName(pyValue) + " to string is not possible.";
	setValueError(msg,m_strict);
#ifdef _DEBUG
	cerr << "PyTypeConversions::PyValue_To_String failed. " << msg << endl;
#endif	
	return std::string();
}

/*			 			C Values to Py Values				  		*/


PyObject*
PyTypeConversions::PyValue_From_CValue(const char* cValue) const
{
	// returns new reference
#ifdef _DEBUG
	if (!cValue) {
		std::string msg = "PyTypeConversions::PyValue_From_CValue: Null pointer encountered while converting from const char* .";
		cerr << msg << endl;
		setValueError(msg,m_strict);
		return NULL;
	}
#endif
	PyObject *pyValue = PyString_FromString(cValue);
	if (!pyValue)
	{
		if (PyErr_Occurred()) {PyErr_Print(); PyErr_Clear();}
		setValueError("Error while converting from char* or string.",m_strict);
#ifdef _DEBUG
		cerr << "PyTypeConversions::PyValue_From_CValue: Interpreter failed to convert from const char*" << endl;
#endif
		return NULL;
	}
	return pyValue;
}

PyObject*
PyTypeConversions::PyValue_From_CValue(size_t cValue) const
{
	// returns new reference
	PyObject *pyValue = PyInt_FromSsize_t((Py_ssize_t)cValue);
	if (!pyValue)
	{
		if (PyErr_Occurred()) {PyErr_Print(); PyErr_Clear();}
		setValueError("Error while converting from size_t.",m_strict);
#ifdef _DEBUG
		cerr << "PyTypeConversions::PyValue_From_CValue: Interpreter failed to convert from size_t" << endl;
#endif
		return NULL;
	}
	return pyValue;
}

PyObject*
PyTypeConversions::PyValue_From_CValue(double cValue) const
{
	// returns new reference
	PyObject *pyValue = PyFloat_FromDouble(cValue);
	if (!pyValue)
	{
		if (PyErr_Occurred()) {PyErr_Print(); PyErr_Clear();}
		setValueError("Error while converting from float or double.",m_strict);
#ifdef _DEBUG
		cerr << "PyTypeConversions::PyValue_From_CValue: Interpreter failed to convert from float or double" << endl;
#endif
		return NULL;
	}
	return pyValue;
}

PyObject*
PyTypeConversions::PyValue_From_CValue(bool cValue) const
{
	// returns new reference
	PyObject *pyValue = PyBool_FromLong((long)cValue);
	if (!pyValue)
	{
		if (PyErr_Occurred()) {PyErr_Print(); PyErr_Clear();}
		setValueError("Error while converting from bool.",m_strict);
#ifdef _DEBUG
		cerr << "PyTypeConversions::PyValue_From_CValue: Interpreter failed to convert from bool" << endl;
#endif
		return NULL;
	}
	return pyValue;
}


/*			 			Sequence Types to C++ Types	    		  	*/

//convert Python list to C++ vector of strings
std::vector<std::string> 
PyTypeConversions::PyValue_To_StringVector (PyObject *pyList) const 
{
	
	std::vector<std::string> Output;
	std::string ListElement;
	PyObject *pyString = NULL;
	
	if (PyList_Check(pyList)) {

		for (Py_ssize_t i = 0; i < PyList_GET_SIZE(pyList); ++i) {
			//Get next list item (Borrowed Reference)
			pyString = PyList_GET_ITEM(pyList,i);
			ListElement = (string) PyString_AsString(PyObject_Str(pyString));
			Output.push_back(ListElement);
		}
		return Output;
	}

// #ifdef _DEBUG
// 	cerr << "PyTypeConversions::PyValue_To_StringVector: Warning: Value is not list of strings." << endl;
// #endif

	/// Assume a single value that can be casted as string 
	/// this allows to write e.g. Feature.label = 5.2 instead of ['5.2']
	Output.push_back(PyValue_To_String(pyList));
	if (m_error) {
		std::string msg = "Value is not list of strings nor can be casted as string. ";
		setValueError(msg,m_strict);
#ifdef _DEBUG
		cerr << "PyTypeConversions::PyValue_To_StringVector failed. " << msg << endl;
#endif
	}
	return Output;
}

//convert PyFeature.value (typically a list or numpy array) to C++ vector of floats
std::vector<float> 
PyTypeConversions::PyValue_To_FloatVector (PyObject *pyValue) const 
{

#ifdef HAVE_NUMPY
if (m_numpyInstalled) 
{
	// there are four types of values we may receive from a numpy process:
	// * a python scalar, 
	// * an array scalar, (e.g. numpy.float32)
	// * an array with nd = 0  (0D array)
	// * an array with nd > 0

	/// check for scalars
	if (PyArray_CheckScalar(pyValue) || PyFloat_Check(pyValue)) {

		std::vector<float> Output;

		// we rely on the behaviour the scalars are either floats
		// or support the number protocol
		// TODO: a potential optimisation is to handle them directly
		Output.push_back(PyValue_To_Float(pyValue));
		return Output;
	}

	/// numpy array
	if (PyArray_CheckExact(pyValue)) 
		return PyArray_To_FloatVector(pyValue);
}
#endif

	/// python list of floats (backward compatible)
	if (PyList_Check(pyValue)) {
		return PyList_To_FloatVector(pyValue);
	}

	std::vector<float> Output;
	
	/// finally assume a single value supporting the number protocol 
	/// this allows to write e.g. Feature.values = 5 instead of [5.00]
	Output.push_back(PyValue_To_Float(pyValue));
	if (m_error) {
		std::string msg = "Value is not list or array of floats nor can be casted as float. ";
		setValueError(msg,m_strict);
#ifdef _DEBUG
	cerr << "PyTypeConversions::PyValue_To_FloatVector failed. " << msg << endl;
#endif
	}
	return Output;
}

//convert a list of python floats
std::vector<float> 
PyTypeConversions::PyList_To_FloatVector (PyObject *inputList) const 
{
	std::vector<float> Output;
	
#ifdef _DEBUG
	// This is a low level function normally called from 
	// PyValue_To_FloatVector(). Checking for list is not required.
	if (!PyList_Check(inputList)) {
		std::string msg = "Value is not list.";
		setValueError(msg,true);
		cerr << "PyTypeConversions::PyList_To_FloatVector failed. " << msg << endl;
		return Output; 
	} 
#endif

	float ListElement;
	PyObject *pyFloat = NULL;
	PyObject **pyObjectArray = PySequence_Fast_ITEMS(inputList);

	for (Py_ssize_t i = 0; i < PyList_GET_SIZE(inputList); ++i) {

		// pyFloat = PyList_GET_ITEM(inputList,i);
		pyFloat = pyObjectArray[i];

#ifdef _DEBUG
		if (!pyFloat) {
			if (PyErr_Occurred()) {PyErr_Print(); PyErr_Clear();}
			cerr << "PyTypeConversions::PyList_To_FloatVector: Could not obtain list element: " 
			<< i << " PyList_GetItem returned NULL! Skipping value." << endl;
			continue;
		}
#endif		

		// ListElement = (float) PyFloat_AS_DOUBLE(pyFloat);
		ListElement = PyValue_To_Float(pyFloat);
		

#ifdef _DEBUG_VALUES
		cerr << "value: " << ListElement << endl;
#endif
		Output.push_back(ListElement);
	}
	return Output;
}

// if numpy is not installed this will not be called, 
// therefor we do not check again
#ifdef HAVE_NUMPY 
std::vector<float> 
PyTypeConversions::PyArray_To_FloatVector (PyObject *pyValue) const 
{
	std::vector<float> Output;
	
#ifdef _DEBUG
	// This is a low level function, normally called from 
	// PyValue_To_FloatVector(). Checking the array here is not required.
	if (!PyArray_Check(pyValue)) {
		std::string msg = "Object has no array conversions.";
		setValueError(msg,true);
		cerr << "PyTypeConversions::PyArray_To_FloatVector failed. " << msg << endl;
		return Output; 
	} 
#endif

	PyArrayObject* pyArray = (PyArrayObject*) pyValue;
	PyArray_Descr* descr = PyArray_DESCR(pyArray);
	
	/// check raw data and descriptor pointers
	if (PyArray_DATA(pyArray) == 0 || descr == 0) {
		std::string msg = "NumPy array with NULL data or descriptor pointer encountered.";
		setValueError(msg,m_strict);
#ifdef _DEBUG
		cerr << "PyTypeConversions::PyArray_To_FloatVector failed. Error: " << msg << endl;
#endif		
		return Output;
	}

	/// check dimensions
	if (PyArray_NDIM(pyArray) != 1) {
		std::string msg = "NumPy array must be a one dimensional vector.";
		setValueError(msg,m_strict);
#ifdef _DEBUG
		cerr << "PyTypeConversions::PyArray_To_FloatVector failed. Error: " << msg << " Dims: " << (int) PyArray_NDIM(pyArray) << endl;
#endif	
		return Output;
	}

#ifdef _DEBUG_VALUES
	cerr << "PyTypeConversions::PyArray_To_FloatVector: Numpy array verified." << endl;
#endif
	
	/// check strides (useful if array is not continuous)
	size_t strides =  *((size_t*) PyArray_STRIDES(pyArray));
    
	/// convert the array
	switch (descr->type_num)
	{
		case NPY_FLOAT : // dtype='float32'
			return PyArray_Convert<float,float>(PyArray_DATA(pyArray),PyArray_DIMS(pyArray)[0],strides);
		case NPY_DOUBLE : // dtype='float64'
			return PyArray_Convert<float,double>(PyArray_DATA(pyArray),PyArray_DIMS(pyArray)[0],strides);
		case NPY_INT : // dtype='int'
			return PyArray_Convert<float,int>(PyArray_DATA(pyArray),PyArray_DIMS(pyArray)[0],strides);
		case NPY_LONG : // dtype='long'
			return PyArray_Convert<float,long>(PyArray_DATA(pyArray),PyArray_DIMS(pyArray)[0],strides);
		default :
			std::string msg = "Unsupported value type in NumPy array object.";
			setValueError(msg,m_strict);
#ifdef _DEBUG
			cerr << "PyTypeConversions::PyArray_To_FloatVector failed. Error: " << msg << endl;
#endif			
			return Output;
	}
}
#endif



/*			   			  	Error handling		   			  		*/

void
PyTypeConversions::setValueError (std::string message, bool strict) const
{
	m_error = true;
	m_errorQueue.push(ValueError(message,strict));
}

/// return a reference to the last error or creates a new one.
ValueError&
PyTypeConversions::lastError() const 
{
	m_error = false;
	if (!m_errorQueue.empty()) return m_errorQueue.back();
	else {
		m_errorQueue.push(ValueError("Type conversion error.",m_strict));
		return m_errorQueue.back();
	}
}

/// helper function to iterate over the error message queue:
/// pops the oldest item
ValueError 
PyTypeConversions::getError() const
{
	if (!m_errorQueue.empty()) {
		ValueError e = m_errorQueue.front();
		m_errorQueue.pop();
		if (m_errorQueue.empty()) m_error = false;
		return e;
	}
	else {
		m_error = false;
		return ValueError();
	}
}

/*			   			  	Utilities						  		*/

/// get the type name of an object
std::string
PyTypeConversions::PyValue_Get_TypeName(PyObject* pyValue) const
{
	PyObject *pyType = PyObject_Type(pyValue);
	if (!pyType) 
	{
		cerr << "Warning: Object type name could not be found." << endl;
		if (PyErr_Occurred()) {PyErr_Print(); PyErr_Clear();}
		return std::string ("< unknown type >");
	}
	PyObject *pyString = PyObject_Str(pyType);
	if (!pyString)
	{
		cerr << "Warning: Object type name could not be found." << endl;
		if (PyErr_Occurred()) {PyErr_Print(); PyErr_Clear();}
		Py_CLEAR(pyType);
		return std::string ("< unknown type >");
	}
	char *cstr = PyString_AS_STRING(pyString);
	if (!cstr)
	{
		cerr << "Warning: Object type name could not be found." << endl;
		if (PyErr_Occurred()) {PyErr_Print(); PyErr_Clear();}
		Py_DECREF(pyType);
		Py_CLEAR(pyString);
		return std::string("< unknown type >");
	}
	Py_DECREF(pyType);
	Py_DECREF(pyString);
	return std::string(cstr);
	
}