使用Cython从标头导出常量

问题描述

我正在使用Cython包装C库。 C库的头文件定义了许多常量，因此在我的cython模块中，我有类似以下内容：

I'm using Cython to wrap a C library. The C library's header file defines a number of constants, so in my cython module, I have something like:

cdef extern from "lib.h":
    cdef int CONST_A = 0
    cdef int CONST_B = 1

编译扩展名时，常量在Python中不可用。我试图做这样的事情，但是似乎没有用：

When I compile the extension, the constants are not available in Python. I tried doing something like this, but it did not seem to work:

cdef extern from "lib.h":
    cdef int CONST_A = 0
    cdef int CONST_B = 1

CONST_A = CONST_A
CONST_B = CONST_B

关于如何使这些常量在Python中可用的任何想法？

Any ideas on how to make these constants available in Python?

推荐答案

您说得对，因为Cython似乎有一个洞。

You're right in that there seems to be a hole in Cython there.

我可以声明 cpdef int CONST_C = 3 并且可以编译，但在Python中不可见。这似乎是一个错误-如果它接受语法，则应该对其进行合理的处理。

I can declare cpdef int CONST_C = 3 and it compiles but isn't visible from Python. That would seem to be a bug -- if it accepts the syntax, it should do something reasonable with it.

似乎起作用的一件事是：

One thing that did seem to work is this:

cpdef enum:
    CONST_A = 0
    CONST_B = 1

这可能对您的情况足够好，但似乎在许多用例中都可以很好地工作-也许这就是为什么该bug并非如此没注意到吗？

That may or may not be good enough for your case, but it seems it would work well for many use-cases -- maybe it's why the bug wasn't noticed?

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