我有一个类将vector作为参数（二进制文件内容）。
我想将python'st'类型转换为unsigned char的向量，但仅适用于我的一个类方法。
BOOST_PYTHON_MODULE(hello) { class_<Hello>("Hello").
// This method takes a string as parameter and print it
.def("printChar", &Hello::printChar)
// This method takes a vector<unsigned char> parameter
.def("storeFile", &Hello::storeFile) }
使用自定义转换器似乎是我需要的但是如果我修改我的boost :: python :: converter :: registry它将修改我对printChar的所有调用以及所有传递字符串的python方法将参数转换为vector 。
如何注册per-method转换器？
答案 0 :(得分：16)
这个问题有两种方法：
Hello.storeFile，接受boost::python::str，从字符串构造std::vector<unsigned char>，并委托给C ++ Hello::storeFile成员函数。使用辅助函数不会影响任何其他导出函数。因此，python字符串和std::vector<unsigned char>之间的转换只会发生在Hello.storeFile。
void Hello_storeFile(Hello& self, boost::python::str str)
{
std::cout << "Hello_storeFile" << std::endl;
// Obtain a handle to the string.
const char* begin = PyString_AsString(str.ptr());
// Delegate to Hello::storeFile().
self.storeFile(std::vector<unsigned char>(begin, begin + len(str)));
}
...
BOOST_PYTHON_MODULE(hello)
{
namespace python = boost::python;
python::class_<Hello>("Hello")
// This method takes a string as parameter and print it
.def("printChar", &Hello::printChar)
// This method takes a vector<unsigned char> parameter
.def("storeFile", &Hello_storeFile)
;
}
转换器注册有三个部分：
PyObject是否可转换的函数。返回NULL表示PyObject无法使用已注册的转换器。PyObject构造C ++类型。仅当converter(PyObject)未返回NULL时才会调用此函数。因此，对于给定的C ++类型，如果converter(PyObject)返回非NULL值，则construct(PyObject)将创建C ++类型。 C ++类型作为注册表的一个键，因此Boost.Python不应执行非预期的转换。
在问题的上下文中，我们想要std::vector<unsigned char>的转换器，converter(PyObject)如果NULL是PyObject则PyString返回非converter(PyObject)，PyObject 1}}将使用std::vector<unsigned char>来创建和填充std::vector<unsigned char>。仅当导出的C ++函数具有std::string（或const引用）参数且python提供的参数是字符串时，才会发生此转换。因此，此自定义转换器不会影响具有#include <iostream>
#include <list>
#include <string>
#include <vector>
#include <boost/foreach.hpp>
#include <boost/python.hpp>
class Hello
{
public:
void printChar(const std::string& str)
{
std::cout << "printChar: " << str << std::endl;
}
void storeFile(const std::vector<unsigned char>& data)
{
std::cout << "storeFile: " << data.size() << ": ";
BOOST_FOREACH(const unsigned char& c, data)
std::cout << c;
std::cout << std::endl;
}
};
/// @brief Type that allows for conversions of python strings to
// vectors.
struct pystring_converter
{
/// @note Registers converter from a python interable type to the
/// provided type.
template <typename Container>
pystring_converter&
from_python()
{
boost::python::converter::registry::push_back(
&pystring_converter::convertible,
&pystring_converter::construct<Container>,
boost::python::type_id<Container>());
return *this;
}
/// @brief Check if PyObject is a string.
static void* convertible(PyObject* object)
{
return PyString_Check(object) ? object : NULL;
}
/// @brief Convert PyString to Container.
///
/// Container Concept requirements:
///
/// * Container::value_type is CopyConstructable from char.
/// * Container can be constructed and populated with two iterators.
/// I.e. Container(begin, end)
template <typename Container>
static void construct(
PyObject* object,
boost::python::converter::rvalue_from_python_stage1_data* data)
{
namespace python = boost::python;
// Object is a borrowed reference, so create a handle indicting it is
// borrowed for proper reference counting.
python::handle<> handle(python::borrowed(object));
// Obtain a handle to the memory block that the converter has allocated
// for the C++ type.
typedef python::converter::rvalue_from_python_storage<Container>
storage_type;
void* storage = reinterpret_cast<storage_type*>(data)->storage.bytes;
// Allocate the C++ type into the converter's memory block, and assign
// its handle to the converter's convertible variable. The C++
// container is populated by passing the begin and end iterators of
// the python object to the container's constructor.
const char* begin = PyString_AsString(object);
data->convertible = new (storage) Container(
begin, // begin
begin + PyString_Size(object)); // end
}
};
BOOST_PYTHON_MODULE(hello)
{
namespace python = boost::python;
// Register PyString conversions.
pystring_converter()
.from_python<std::vector<unsigned char> >()
.from_python<std::list<char> >()
;
python::class_<Hello>("Hello")
// This method takes a string as parameter and print it
.def("printChar", &Hello::printChar)
// This method takes a vector<unsigned char> parameter
.def("storeFile", &Hello::storeFile)
;
}
参数的导出函数。
这是一个完整的例子。我选择使转换器通用，以允许从python字符串构造多个类型。凭借其链接支持，它应该具有与其他Boost.Python类型相同的感觉。
>>> from hello import Hello
>>> h = Hello()
>>> h.printChar('abc')
printChar: abc
>>> h.storeFile('def')
storeFile: 3: def
>>> h.storeFile([c for c in 'def'])
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
Boost.Python.ArgumentError: Python argument types in
Hello.storeFile(Hello, list)
did not match C++ signature:
storeFile(Hello {lvalue}, std::vector<unsigned char,
std::allocator<unsigned char> >)
示例用法：
{{1}}
有关自定义转换器和C ++容器的更多信息，请考虑阅读this answer。