如何在Cython中创建固定长度,可变的Python对象数组？

Question

我需要有一个python对象数组用于创建一个trie数据结构.我需要一个像元组一样固定长度的结构,像列表一样可变.我不想用一个列表,因为我希望能够确保该列表是正好合适的大小(如果它开始分配额外的元素,内存开销很可能会迅速增加为线索变大).有没有办法做到这一点？我尝试创建一个对象数组:

cdef class TrieNode:
    cdef object members[32]

......但是这给了一个错误:

Error compiling Cython file:
------------------------------------------------------------
...
cdef class TrieNode:
    cdef object members[32]
                      ^
------------------------------------------------------------

/Users/jason/src/pysistence/source/pysistence/trie.pyx:2:23: Array element cannot be a Python object

做我想做的最好的方法是什么？

Answer 1

我不知道最好的解决方案,但这是一个解决方案:

from cpython.ref cimport PyObject, Py_XINCREF, Py_XDECREF

DEF SIZE = 32

cdef class TrieNode:
    cdef PyObject *members[SIZE]

    def __cinit__(self):
        cdef object temp_object
        for i in range(SIZE):
            temp_object = int(i)
            # increment its refcount so it's not gc'd.
            # We hold a reference to the object and are responsible for
            # decref-ing it in __dealloc__.
            Py_XINCREF(<PyObject*>temp_object)
            self.members[i] = <PyObject*>temp_object

    def __init__(self):
        # just to show that it works...
        for i in range(SIZE):
            print <object>self.members[i]

    def __dealloc__(self):
        # make sure we decref the members elements.
        for i in range(SIZE):
            Py_XDECREF(self.members[i])
            self.members[i] = NULL

Cython object是自动重新计算的PyObject *.PyObject *只要您负责重新计算小虫子,您就可以随时滚动自己的阵列.这可能是非平凡案件的主要问题.

Answer 2

这个怎么样？

class TrieNode():
   def __init__(self, length = 32):
      self.members = list()
      self.length = length
      for i in range(length):
         self.members.append(None)

   def set(self, idx, item):
      if idx < self.length and idx >= 0:
         self.members[idx] = item
      else:
         print "ERROR: Specified index out of range."
         # Alternately, you could raise an IndexError.

   def unset(self, idx):
      if idx < self.length and idx >= 0:
         self.members[idx] = None
      else:
         raise IndexError("Specified index out of range (0..%d)." % self.length)