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在Cython中定义字符串数组

cython

2

Brad Solomon · 技术社区 · 7 年前

在Cython中定义字符串数组的规范有效方法是什么? 具体来说,我想定义一个固定长度的常量数组 char

在C中,这将是:

/* cletters.c */
#include <stdio.h>

int main(void)
{
    const char *headers[3] = {"to", "from", "sender"};
    int i;
    for (i = 0; i < 3; i++)
        printf("%s\n", headers[i]);
}

在Cython中尝试:

# cython: language_level=3
# letters.pyx

cpdef main():
    cdef const char *headers[3] = {"to", "from", "sender"}
    print(headers)

(cy) $ python3 ./setup.py build_ext --inplace --quiet
cpdef main():
    cdef const char *headers[3] = {"to", "from", "sender"}
                               ^
------------------------------------------------------------

letters.pyx:5:32: Syntax error in C variable declaration

1 回复 | 直到 7 年前

1

4

ead 7 年前

您需要两行:

%%cython
cpdef main():
    cdef const char *headers[3] 
    headers[:] = ['to','from','sender`]       
    print(headers)

有点违反直觉的是,将unicode字符串(Python3!)分配给 char* . 这是Cython的怪癖之一。另一方面,当只使用一个值初始化所有内容时,需要bytes对象:

%%cython
cpdef main():
    cdef const char *headers[3] 
    headers[:] = b'init_value`  ## unicode-string 'init_value' doesn't work.     
    print(headers)

另一种选择是以下oneliner:

%%cython
cpdef main():
    cdef const char **headers=['to','from','sender`]

    print(headers[0], headers[1], headers[2])

这与上述不完全相同,并导致以下C代码:

  char const **__pyx_v_headers;
  ...
  char const *__pyx_t_1[3];
  ...
  __pyx_t_1[0] = ((char const *)"to");
  __pyx_t_1[1] = ((char const *)"from");
  __pyx_t_1[2] = ((char const *)"sender");
  __pyx_v_headers = __pyx_t_1;

__pyx_v_headers char ** 缺点是 print(headers)

2

3

Dev Aggarwal 7 年前

对于python3 Unicode字符串,这是可能的-

cdef Py_UNICODE* x[2] 
x = ["hello", "worláªd"]

或

cdef Py_UNICODE** x
x = ["hello", "worláªd"]