我正在尝试使用ctypes在Python2.7中加载DLL。DLL是使用Fortran编写的，并且其中包含多个子例程。我能够成功设置几个导出的函数，long并将这些函数和double指针作为参数。

import ctypes as C
import numpy as np

dll = C.windll.LoadLibrary('C:\\Temp\\program.dll')
_cp_from_t = getattr(dll,"CP_FROM_T")
_cp_from_t.restype = C.c_double
_cp_from_t.argtypes = [C.POINTER(C.c_longdouble),np.ctypeslib.ndpointer(C.c_longdouble)]

# Mixture Rgas function
_mix_r = getattr(dll,"MIX_R")
_mix_r.restype = C.c_double
_mix_r.argtypes = [np.ctypeslib.ndpointer(dtype=C.c_longdouble)]

def cp_from_t(composition,temp):
    """ Calculates Cp in BTU/lb/R given a fuel composition and temperature.

    :param composition: numpy array containing fuel composition
    :param temp: temperature of fuel
    :return: Cp
    :rtype : float
    """
    return _cp_from_t(C.byref(C.c_double(temp)),composition)

def mix_r(composition):
    """Return the gas constant for a given composition.
    :rtype : float
    :param composition: numpy array containing fuel composition
    """
    return _mix_r(composition)

# At this point,I can just pass a numpy array as the composition and I can get the 
# calculated values without a problem
comps = np.array([0,12.0,23.0,33.0,10,5.0])
temp = 900.0

cp = cp_from_t(comps,temp)
rgas = mix_r(comps)

到现在为止还挺好。

当我尝试调用
另一个Function2需要一些字符串作为输入的子例程时，就会出现问题。字符串都是固定长度（255），并且它们还会要求每个字符串参数的长度。

该功能在Fortran中实现如下：

Subroutine FUNCTION2(localBasePath,localTempPath,InputFileName,Model,DataArray,ErrCode)
!DEC$ ATTRIBUTES STDCALL,REFERENCE,ALIAS:'FUNCTION2',DLLEXPORT :: FUNCTION2
Implicit None
Character *255 localBasePath,InputFileName
Integer   *4  Model(20),ErrCode(20)
Real      *8  DataArray(900)

Python中的函数原型设置如下

function2 = getattr(dll,'FUNCTION2')
function2.argtypes = [C.POINTER(C.c_char_p),C.c_long,C.POINTER(C.c_char_p),np.ctypeslib.ndpointer(C.c_long,flags='F_CONTIGUOUS'),np.ctypeslib.ndpointer(C.c_double,flags='F_CONTIGUOUS')]

我称它为：

base_path = "D:\\Users\\xxxxxxx\\Documents\\xxxxx\\".ljust(255)
temp_path = "D:\\Users\\xxxxxxx\\Documents\\xxxxx\\temp".ljust(255)
inp_file = "inp.txt".ljust(255)

function2(C.byref(C.c_char_p(base_path)),C.c_long(len(base_path)),C.byref(C.c_char_p(temp_dir)),C.c_long(len(temp_dir))),C.byref(C.c_char_p(inp_file)),C.c_long(len(inp_file)),model_array,data_array,error_array)

字符串本质上是路径。该函数Function2无法识别路径，并在错误消息的末尾显示一些不可读的字符，例如：

forrtl: severe (43): file name specification error,unit 16,D:\Users\xxxxxxx\Documents\xxxxx\ωa。

我想要的功能是D:\Users\xxxxxxx\Documents\xxxxx\。显然，字符串传递不正确。

我读过Python使用NULL终止的字符串。将字符串传递到Fortran dll时会出现问题吗？如果是这样，我该如何解决？

有什么建议吗？

echo "some
different
lines
" | for i ; do 
  echo do something with $i; 
done

解决方法

echo "some
different
lines
" | for i in $(cat) ; do
    ...
done

a=($(echo "some
different
lines
"))
for i in "${a[@]}"; do
    ...
done

unsigned int SetParams(unsigned int count,const char **params)

import ctypes as ct
lib = ct.cdll.LoadLibrary(''...'')
lib.SetParams.restype  = ct.c_uint
lib.SetParams.argtypes = [ct.c_uint,ct.POINTER(ct.c_char_p)]

def setParameters(strParamList):
    numParams    = len(strParamList)
    strArrayType = ct.c_char_p * numParams
    strArray     = strArrayType()
    for i,param in enumerate(strParamList):
        strArray[i] = param
    lib.SetParams(numParams,strArray)

解决方法

setParameters([''abc'',''def'',''ghi''])

TypeError: unsupported operand type(s) for +: ''geoprocessing value object'' and ''str'' 
 if self.params[0].value:
        mypath=self.params[0].value #
        cpath=mypath+os.sep+dataset
        arcpy.env.workspace =cpath
修改如下：
 if self.params[0].value:
        mypath=str(self.params[0].value) #
        cpath=mypath+os.sep+dataset
        arcpy.env.workspace =cpath

我最近遇到了TypeError异常，发现它很难调试。我最终将其简化为这个小测试用例：

>>> "{:20}".format(b"hi")
Traceback (most recent call last):
  File "<stdin>",line 1,in <module>
TypeError: non-empty format string passed to object.__format__

无论如何，这对我来说不是很明显。我的代码的解决方法是将字节字符串解码为unicode：

 >>> "{:20}".format(b"hi".decode("ascii"))
 'hi                  '

此异常的含义是什么？有没有一种方法可以使它更清晰？