Question

我想使用PySide来定义基本的QT类以及C ++和python之间的映射，但是要在独立的python代码和使用boost :: python的嵌入式python中这样做。

首先，模块定义和类返回QPointF：

QPointF  X::getY() { 
  return QPointF(); 
}    

BOOST_PYTHON_MODULE(myBoostPythonModule)
{
// is there some magic init/register commands to put here?
boost::python::api::object module     = import("__main__");
boost::python::api::object name_space = module.attr("__dict__");
boost::python::exec("from PySide.QtCore import *",name_space,name_space);
boost::python::exec("import sys,os\nprint(sys.modules)",name_space,name_space);

class_<X, boost::noncopyable>(
            "X", init<const char*>())
        .def("getY",&X::getY)
        ;
}

现在，应用程序的嵌入式python代码，最后一行是失败的，我想知道如何解决：

execute("import myBoostPythonModule");     // OK
execute("x=myBoostPythonModule.X('foo')"); // OK

execute("w=QPointF()\nprint(w)");          // OK
// PySide.QtCore.QPointF(0.000000, 0.000000)

execute("y=x.getY()");                     // FAIL:
// TypeError: No to_python (by-value) converter found for C++ type: QPointF

这里发生了什么，我可以创建一个QPointF，但这个名字在某种程度上并没有绑定到python和c ++之间？我是否错过了模块中的一些导入来告诉它从PySide导入？

Answer 1

PySide使用Shiboken提供其Qt绑定。 Shiboken生成支持其自己的类型转换系统的Python C API绑定。这些转换的知识存在于Shiboken生成的绑定中，而不是Python类型系统中。因此，PySide知道如何将QPointF对象转换为C ++ / Python; Python的类型系统没有。

当一个对象转换为使用Boost.Python公开的函数时，Boost.Python将检查其注册表中是否有适当的类型转换器。这些转换器为Boost.Python提供了有关如何通过Boost.Python公开的类型转换为C ++ / Python的知识。因此，当Boost.Python尝试将QPointF C ++类型返回给Python时，它会抛出异常，因为转换尚未在Boost.Python中注册。

以下是带注释的代码：

import myBoostPythonModule
from PySide.QtCore import *
...
x=myBoostPythonModule.X('foo') # Boost.Python knows how to convert C++ X
                               # to Python X.  Python's type system does not.

w=QPointF()                    # Shiboken knows how to convert C++ QPointF to
                               # Python QPointF.  Python's type system does not.
print(w)                       # Shiboken knows how to represent C++ QPointF as
                               # a string.

y=x.getY()                     # Boost.Python knows how to invoke X::getY(),
                               # but only Shiboken knows how to convert C++
                               # QPointF to Python QPointF.  Thus, the TypeError
                               # exception is raised.

就另一种实现而言，可以实现Boost.Python的converters。扩展Shiboken type converter example，下面是使用Shiboken旧类型转换器实现的Boost.Python转换器的完整示例。我会使用新的Shiboken类型转换器API，但我不清楚它是基于文档的内容。

#include <iostream>

#include <boost/python.hpp>

/// @brief Mockup Complex class from Shiboken documentation.
class Complex
{
public:
  Complex(double real, double imaginary)
    : real_(real),
      imaginary_(imaginary)
  {}

  double real() const      { return real_;      }
  double imaginary() const { return imaginary_; }

private:
  double real_;
  double imaginary_;
};

/// @brief Mocked up Shiboken converter.
namespace Shiboken {

template <typename> struct Converter;

template <> struct Converter<Complex>
{
public:
  // ...

  static inline bool isConvertible(PyObject* pyObj)
  {
    std::cout << "Shiboken::Converter<Complex>::isConvertible()" << std::endl;
    return PyComplex_Check(pyObj);
  }

  // ...

  static inline PyObject* toPython(const Complex& cpx)
  {
    std::cout << "Shiboken::Converter<Complex>::toPython()" << std::endl;
    return PyComplex_FromDoubles(cpx.real(), cpx.imaginary());
  }

  static inline Complex toCpp(PyObject* pyobj)
  {
    std::cout << "Shiboken::Converter<Complex>::toCpp()" << std::endl;
    double real      =  PyComplex_RealAsDouble(pyobj);
    double imaginary =  PyComplex_ImagAsDouble(pyobj);
    return Complex(real, imaginary);
  }
};
} // namespace Shiboken

/// @brief Type used to convert a complex to Python.
struct complex_converter_to_python
{
  static PyObject* convert(const Complex& c)
  {
    // Delegate to Shiboken.
    std::cout << "complex_converter_to_python::convert()" << std::endl;
    return Shiboken::Converter<Complex>::toPython(c);
  }
};

/// @brief Type that registers a Python Complex type to C++
///        Complex when passing through Boost.Python.
struct complex_converter_from_python
{
  /// @note Registers converter from a python complex to C++ complex.
  complex_converter_from_python()
  {
    boost::python::converter::registry::push_back(
      &complex_converter_from_python::convertible,
      &complex_converter_from_python::construct,
      boost::python::type_id<Complex>());
  }

  /// @brief Check if PyObject is a Complex.
  static void* convertible(PyObject* object)
  {
    // Delegate to Shiboken.  Based on the documentation, the
    // isConvertible function is gone, so explicit checking may
    // be required based on the version of Shiboken.
    std::cout << "complex_converter_from_python::convertible()" << std::endl;
    return Shiboken::Converter<Complex>::isConvertible(object)
      ? object 
      : NULL;
  }

  /// @brief Convert Python Complex to C++ Complex.
  static void construct(
    PyObject* object,
    boost::python::converter::rvalue_from_python_stage1_data* data)
  {
    // Obtain a handle to the memory block that the Boost.Python
    // converter has allocated for the C++ type.
    namespace python = boost::python;
    typedef python::converter::rvalue_from_python_storage<Complex>
                                                                storage_type;
    void* storage = reinterpret_cast<storage_type*>(data)->storage.bytes;

    // In-place construct a Complex type via copy-constructor, passing
    // in a Complex created from Shiboken.
    std::cout << "complex_converter_from_python::construct()" << std::endl;
    data->convertible = new (storage) Complex(
      Shiboken::Converter<Complex>::toCpp(object));
  }
};

/// @brief Factory function used to exercise to-python conversion.
Complex make_complex(double real, double imaginary)
{
  return Complex(real, imaginary);
}

/// @brief Printing function used to exercise from-python converison.
void print_complex(const Complex& c)
{
  std::cout << "In print_complex: "
            << c.real() << ", "
            << c.imaginary() << std::endl;
}

BOOST_PYTHON_MODULE(example)
{
  namespace python = boost::python;

  // Register Complex from python converter.
  complex_converter_from_python();

  // Register Complex to python converter.
  python::to_python_converter<
    Complex,
    complex_converter_to_python>();

  python::def("make_complex",  &make_complex);
  python::def("print_complex", &print_complex);
}

及其用法：

>>> import example
>>> x = example.make_complex(4, 2)
complex_converter_to_python::convert()
Shiboken::Converter<Complex>::toPython()
>>> example.print_complex(x)
complex_converter_from_python::convertible()
Shiboken::Converter<Complex>::isConvertible()
complex_converter_from_python::construct()
Shiboken::Converter<Complex>::toCpp()
In print_complex: 4, 2

替代方案，虽然不是最优雅的方法，但可以使用Boost.Python公开的函数使用boost::python::object类型，并通过Python语句与对象进行交互。类似于：

boost::python::object X::getY()
{ 
  return boost::python::exec("QPointF()", ...); 
}

上面的代码将使Python实例化一个QPointF Python对象，该对象将委托给Shiboken的类型系统。当X::getY()返回一个通用对象时，当对象句柄从C ++转换为Python时，Boost.Python不会尝试执行类型转换。

Answer 2

根据之前的回复和我发现的其他信息，这里有一个通用例程，允许将PySide.QtGui.QColor参数传递给boost::python包装的c ++方法，该方法需要{{1输入参数：

QColor&

并从启动函数调用上述内容：

template<class QtGuiClass,int SBK_BOGAN_IDX>
struct QtGui_from_python {
QtGui_from_python() {
  qDebug()<<" registering type: " << typeid(this).name() << " in " << __FUNCTION__;
  boost::python::converter::registry::push_back(
    &convertible,
    &construct,
    boost::python::type_id<QtGuiClass>());
}
static void* convertible(PyObject* obj_ptr) {
    if(!PyObject_TypeCheck(obj_ptr,
            (PyTypeObject*)XSbkPySide_QtGuiTypes[SBK_BOGAN_IDX]))
    {    qDebug()<<"Failed type check!?"; }
    return obj_ptr;
}
static void construct( PyObject* obj_ptr, 
   bp::converter::rvalue_from_python_stage1_data* data)
{
    void* storage = (
    (boost::python::converter::rvalue_from_python_storage<QtGuiClass>*)
    data)->storage.bytes;

    SbkObject* result = reinterpret_cast<SbkObject*>(obj_ptr);
    auto _ptr = (QtGuiClass*) (Shiboken::Object::cppPointer(
                                       result,Py_TYPE(result)));
    new (storage) QtGuiClass(*_ptr);
    qDebug() << "__alloc'd " << typeid(*_ptr).name() <<" at "<<_ptr;
    data->convertible = storage;
}
};

从boost的python模块中的pyside导入类？

2 个答案: