【发布时间】：2020-02-06 10:39:47
【问题描述】：
我正在使用 c_types 将 fortran 库与 python 连接。我在python中初始化结构，将它们传递给填充它们的fortran，然后在python中读回它们。数字数组一切正常，但现在我被字符串数组接口卡住了。
我试过像one 这样的例子，这没问题，但在这种情况下，c_char 数组不在结构中。因此，我尝试修改前面的示例，将 c_char 数组放入结构中。这是我使用的代码，有和没有结构：
Python 代码：
from ctypes import *
lib = CDLL("./libf.so")
if 1:
print(">>> Without structure")
func = getattr(lib, "fortran2py_")
nstring = pointer(c_long(2))
carr = (c_char * 255)()
func.argtypes = [POINTER(c_long), POINTER(c_char)]
print(type(carr))
print('before:',carr)
func(nstring, carr)
str1, str2 = ''.join([v.decode("utf-8") for v in carr]).rstrip("\x00").split("\x00")
print(str1, str2)
class Struct0(Structure):
_fields_ = [
("name", c_char * 255),
]
if 1:
print(">>> With structure")
func = getattr(lib, "fortran2pystr_")
nstring = pointer(c_long(2))
carr = Struct0()
func.argtypes = [POINTER(c_long), POINTER(Struct0)]
print(type(carr.name))
print('before:',carr.name)
func(nstring, byref(carr))
print('after:',carr.name)
Fortran 代码：
module c_interop
use iso_c_binding
implicit none
integer, parameter :: STRLEN = 64
type, bind(c) :: charStr
character(c_char) :: name(255)
end type charStr
contains
subroutine fortran2py(nstring, cstring_p) bind(C, name="fortran2py_")
integer(c_int), intent(in) :: nstring
character(c_char), dimension(*), intent(inout) :: cstring_p
integer :: i, j, ks, kf, n
character(len=STRLEN) :: mystr(2)
mystr(1) = "This is the first string."
mystr(2) = "Wow. Fortran + Python + Strings = Pain !"
ks = 1
do i = 1, nstring
n = len_trim(mystr(i))
kf = ks + (n - 1)
cstring_p(ks:kf) = transfer(mystr(i)(1:n), cstring_p(ks:kf))
cstring_p(kf + 1) = c_null_char
ks = ks + n + 1
enddo
end subroutine fortran2py
subroutine fortran2pystr(nstring, cstring_p) bind(C, name="fortran2pystr_")
integer(c_int), intent(in) :: nstring
type(charStr), intent(inout) :: cstring_p
integer :: i, j, ks, kf, n
character(len=STRLEN) :: mystr(2)
mystr(1) = "This is the first string."
mystr(2) = "Wow. Fortran + Python + Strings = Pain !"
ks = 1
do i = 1, nstring
n = len_trim(mystr(i))
kf = ks + (n - 1)
cstring_p%name(ks:kf) = transfer(mystr(i)(1:n), cstring_p%name(ks:kf))
cstring_p%name(kf + 1) = c_null_char
ks = ks + n + 1
enddo
end subroutine fortran2pystr
end module c_interop
我没有得到任何错误，除了在修改部分，Fortran 应该填充 c_char carr.name 循环在 mystr 的元素上的数组，但结果字符串只包含第一个元素。当carr不是结构体而是直接c_char数组时，python可以读取mystr的所有内容。
输出：
>>> Without structure
<class '__main__.c_char_Array_255'>
before: <__main__.c_char_Array_255 object at 0x151b3b092bf8>
This is the first string. Wow. Fortran + Python + Strings = Pain !
>>> With structure
<class 'bytes'>
before: b''
after: b'This is the first string.'
正如您所见，carr 和 carr.name 的类型也不相同。您知道我修改后的代码有什么问题吗？谢谢！
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