我正在尝试从Python脚本访问存储在Fortran 77公共块中的数据。问题是我不知道这些数据的存储位置。 我正在开发的Python应用程序使用不同的库。这些库包含具有以下指令的函数:
#include <tcsisc_common.inc>
公共区块包含:
C
INTEGER*4 IDEBUG
C
C.... ARRAY DIMENSIONS
DIMENSION IDEBUG(10)
C
C.... COMMON BLOCK
COMMON /TCSD/ IDEBUG
C
在Python部分(在我使用过iPython的例子中),我加载了库:
In [1]: import ctypes
In [2]: _libtcsisc= /home/jfreixa/project/bin/libtcsisc.so
In [3]: _tcsisc = ctypes.CDLL(_libtcsisc, ctypes.RTLD_GLOBAL)
问题在于我不知道如何获得IDEBUG。我尝试了以下内容,但我只是将tcsd作为初始化为0的c_long。
In [4]: tcsd = ctypes.c_int.in_dll(_tcsisc, "TCSD_")
In [5]: tcsd
Out[5]: c_long(0)
In [6]: idebug = ctypes.c_int.in_dll(_tcsisc, "IDEBUG_")
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-6-ee5018286275> in <module>()
----> 1 idebug = ctypes.c_int.in_dll(_tcsisc,'IDEBUG_')
ValueError: ld.so.1: python2.7: fatal: IDEBUG_: can't find symbol
有没有想法正确获取变量?
答案 0 :(得分:3)
根据this page(特别是如何从C访问Fortran公共块)和一些Q/A page关于如何从Python访问C结构,似乎我们可以按如下方式访问公共块(尽管如此可能不是很便携,见下文):
mylib.f90
subroutine fortsub()
implicit none
integer n
common /mycom/ n
print *, "fortsub> current /mycom/ n = ", n
end
编译:
$ gfortran -shared -fPIC -o mylib.so mylib.f90
test.py
from __future__ import print_function
import ctypes
class Mycom( ctypes.Structure ):
_fields_ = [ ( "n", ctypes.c_int ) ]
mylib = ctypes.CDLL( "./mylib.so" )
mycom = Mycom.in_dll( mylib, "mycom_" )
print( " python> modifying /mycom/ n to 777" )
mycom.n = 777
fortsub = mylib.fortsub_
fortsub()
测试:
$ python test.py
python> modifying /mycom/ n to 777
fortsub> current /mycom/ n = 777
请注意,公共块的名称(此处为mycom
)为小写,并附加一个下划线(假设为gfortran)。因为这个约定是依赖于编译器的,所以编写新的Fortran例程来设置/获取公共块中的值(特别是在iso_c_binding
的帮助下)并从Python调用这些例程可能更健壮/可移植(如建议的那样) @innoSPG在第一条评论中。)
包含不同类型和数组的另一个示例可能如下所示:
mylib.f90
subroutine initcom()
implicit none
integer n( 2 ), w !! assumed to be compatible with c_int
real f( 2 ) !! ... with c_float
double precision d( 2 ) !! ... with c_double
common /mycom/ n, f, d, w
print *, "(fort) initializing /mycom/"
n(:) = [ 1, 2 ]
f(:) = [ 3.0, 4.0 ]
d(:) = [ 5.0d0, 6.0d0 ]
w = 7
call printcom()
end
subroutine printcom()
implicit none
integer n( 2 ), w
real f( 2 )
double precision d( 2 )
common /mycom/ n, f, d, w
print *, "(fort) current /mycom/"
print *, " n = ", n
print *, " f = ", f
print *, " d = ", d
print *, " w = ", w
end
test.py
from __future__ import print_function
import ctypes
N = 2
class Mycom( ctypes.Structure ):
_fields_ = [ ( "x", ctypes.c_int * N ),
( "y", ctypes.c_float * N ),
( "z", ctypes.c_double * N ),
( "w", ctypes.c_int ) ]
mylib = ctypes.CDLL( "./mylib.so" )
mycom = Mycom.in_dll( mylib, "mycom_" )
initcom = mylib.initcom_
initcom()
print( " (python) current /mycom/" )
print( " x = ", mycom.x[:] )
print( " y = ", mycom.y[:] )
print( " z = ", mycom.z[:] )
print( " w = ", mycom.w )
print( " (python) modifying /mycom/ ..." )
for i in range( N ):
mycom.x[ i ] = (i + 1) * 10
mycom.y[ i ] = (i + 1) * 100
mycom.z[ i ] = (i + 1) * 0.1
mycom.w = 777
printcom = mylib.printcom_
printcom()
测试:
$ python test.py
(fort) initializing /mycom/
(fort) current /mycom/
n = 1 2
f = 3.0000000 4.0000000
d = 5.0000000000000000 6.0000000000000000
w = 7
(python) current /mycom/
x = [1, 2]
y = [3.0, 4.0]
z = [5.0, 6.0]
w = 7
(python) modifying /mycom/ ...
(fort) current /mycom/
n = 10 20
f = 100.00000 200.00000
d = 0.10000000000000001 0.20000000000000001
w = 777