问题描述
我正在尝试使用cython将c ++类公开给python.我在* .pxd文件中编写了它们的定义，并在* .pyx文件中实现了包装器.但是我在尝试传递给扩展类型的函数指针时遇到了麻烦.这是简化的示例.
I'm trying to expose c++ classes to python using cython. I wrote their definitions in *.pxd file and implemented a wrappers in *.pyx files. But I got stuck trying to pass to a function pointer to the extension type. Here is simplified example.
foo.pyx
from c_foo cimport cFoo
cdef class Foo:
cdef cFoo* _impl
c_foo_holder.pxd
cdef extern from "FooHolder.h":
cdef cppclass cFooHolder:
cFooHolder(cFoo* foo)
foo_holder.pyx
from c_foo_holder cimport cFooHolder
from c_foo cimport cFoo
cdef class FooHolder:
cdef cFooHolder* _impl
def __init__(self, foo):
self._impl = new cFooHolder(<cFoo*>(foo._impl)) # error here
但是在最后一行，我收到错误消息" Python对象无法转换为原始类型的指针".我还尝试了其他几种方法，但没有任何效果:
But on the last line I get error "Python objects cannot be cast to pointers of primitive types". I also tried several other approaches, but nothing worked:
# error: 'Foo' is not a type identifier
from foo import Foo
def __init__(self, Foo foo):
self._impl = new cFooHolder(foo._impl)
# error: 'Foo' is not a type identifier
def __init__(self, foo):
self._impl = new cFooHolder(<Foo>(foo)._impl)
推荐答案
我找到了解决方案.您必须告诉cython foo._impl实际上是cFoo *实例.这可以通过提供Foo定义来实现(例如，在foo.pxd中).之后，您可以将python对象转换为Foo，而cython会知道其_impl字段的类型为cFoo *.
I found the solution. You have to tell cython that foo._impl is really cFoo* instance. That can be achieved by providing Foo definition (e.g. in foo.pxd). Afterwards you are able to cast python object to Foo and cython will know that its _impl field has type cFoo*.
foo.pxd
from c_foo cimport cFoo
cdef class Foo:
cdef cFoo* _impl
foo.pyx
from c_foo cimport cFoo
cdef class Foo:
# methods implementation
c_foo_holder.pxd
cdef extern from "FooHolder.h":
cdef cppclass cFooHolder:
cFooHolder(cFoo* foo)
foo_holder.pyx
from c_foo_holder cimport cFooHolder
from c_foo cimport cFoo
from foo cimport Foo
cdef class FooHolder:
cdef cFooHolder* _impl
def __init__(self, foo):
self._impl = new cFooHolder((<Foo?>foo)._impl)
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