在cdef类中混合cdef和常规python属性 [英] Mixing cdef and regular python attributes in cdef class

问题描述

我正在学习Cython，现在正在尝试。我尝试了基本的cdef类示例程序，并且效果很好。

i am learning Cython and now experimenting with it. I tried the basic cdef class sample program and it works perfectly.

现在我要做的是在cdef类中混合使用cdef和非cdef属性类型，类似这样的

Now what i want to do is have a mix of cdef and non cdef mix of attributes in the cdef class type, something like this

cdef class Context:
    cdef public int byteIndex, bitIndex

    def __init__(self, msg = "", msg_len = 0):
        self.msg = msg 
        self.msg_len = msg_len 
        self.byteIndex = 0
        self.bitIndex = 7

但是一旦实例化对象，我就会出错

but as soon as i instantiate the object i get error

!! AttributeError：'c_asnbase.Context'对象没有属性'msg'

这是否意味着一旦您定义了一个全自定义cdef的python类。 *必须定义cdef属性？

Does this mean once you define a python class with cdef all self.* attributes have to be cdef defined?

推荐答案

这是否意味着一旦您定义了python类， cdef必须将所有self。*属性定义为cdef？

Does this mean once you define a python class with cdef all self.* attributes have to be cdef defined?

是。 文档：

cdef类中的属性的行为与常规类中的属性不同：

Attributes in cdef classes behave differently from attributes in regular classes:

• 所有属性必须在编译时预先声明


• ...

您可以通过将属性定义为object类型来愉快地存储字符串：

You can quite happily store a string by defining the attribute to be of type object:

cdef public object msg

---

内部，原因是 cdef类没有字典，这样可以节省空间并使属性访问更快，但这确实意味着它不能在运行时添加任意属性。这与在普通的Python类中使用 __ slots __ 类似。

---

Internally, the reason for this is that the cdef class does not have a dictionary, which saves space and makes attribute access faster, but it does mean that it cannot have arbitrary attributes added at runtime. This is reasonably similar to using __slots__ in a normal Python class.

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