在 Windows 上，find_library搜索目录中的PATH环境变量，这不是真实的桌面应用程序的搜索顺序 http://msdn.microsoft.com/en-us/library/ms682586#search_order_for_desktop_applications由 Windows 加载程序使用。尤其find_library不包括应用程序目录和当前目录。
调用WindowsSearchPath会更接近，但给定 DLL 也不会更接近激活上下文 https://msdn.microsoft.com/en-us/library/aa374153以及其他 API，例如SetDllDirectory或较新的 APISetDefaultDllDirectories and AddDllDirectory.
鉴于没有简单的方法来复制 Windows 加载程序使用的搜索，只需使用以下任一方法按名称加载 DLLCDLL(cdecl) 或WinDLL（标准调用）：
nidaq_cdecl = ctypes.CDLL('NIDAQmx')
nidaq_stdcall = ctypes.WinDLL('NIDAQmx')
您可以将DLL目录添加到PATH在运行时动态地（与 Linux 加载器的缓存相反）LD_LIBRARY_PATH启动时）。例如，假设您的 DLL 依赖项位于包的“dlls”子目录中。您可以按如下方式添加此目录：
import os
basepath = os.path.dirname(os.path.abspath(__file__))
dllspath = os.path.join(basepath, 'dlls')
os.environ['PATH'] = dllspath + os.pathsep + os.environ['PATH']
或者，您可以使用上下文管理器来调用GetDllDirectory https://msdn.microsoft.com/en-us/library/ms683186 and SetDllDirectory https://msdn.microsoft.com/en-us/library/ms686203临时修改当前工作目录通常占用的搜索槽。请记住，就像修改一样PATH，这会修改全局进程数据，所以使用多线程时要小心。这种方法的一个优点是它不会修改搜索路径CreateProcess用于查找可执行文件。
import os
import ctypes
from ctypes import wintypes
from contextlib import contextmanager
kernel32 = ctypes.WinDLL('kernel32', use_last_error=True)
def check_dword(result, func, args):
if result == 0:
last_error = ctypes.get_last_error()
if last_error != 0:
raise ctypes.WinError(last_error)
return args
def check_bool(result, func, args):
if not result:
last_error = ctypes.get_last_error()
if last_error != 0:
raise ctypes.WinError(last_error)
else:
raise OSError
return args
kernel32.GetDllDirectoryW.errcheck = check_dword
kernel32.GetDllDirectoryW.argtypes = (wintypes.DWORD, # _In_ nBufferLength
wintypes.LPWSTR) # _Out_ lpBuffer
kernel32.SetDllDirectoryW.errcheck = check_bool
kernel32.SetDllDirectoryW.argtypes = (wintypes.LPCWSTR,) # _In_opt_ lpPathName
@contextmanager
def use_dll_dir(dll_dir):
size = newsize = 0
while newsize >= size:
size = newsize
prev = (ctypes.c_wchar * size)()
newsize = kernel32.GetDllDirectoryW(size, prev)
kernel32.SetDllDirectoryW(os.path.abspath(dll_dir))
try:
yield
finally:
kernel32.SetDllDirectoryW(prev)
例如：
if __name__ == '__main__':
basepath = os.path.dirname(os.path.abspath(__file__))
dllspath = os.path.join(basepath, 'dlls')
with use_dll_dir(dllspath):
nidaq = ctypes.CDLL('NIDAQmx')
当然，如果您只想在启动时设置一次 DLL 目录，那么问题就简单得多。只需致电SetDllDirectoryW直接地。
另一种方法是调用LoadLibraryEx与旗帜LOAD_WITH_ALTERED_SEARCH_PATH，这会临时将加载的 DLL 目录添加到搜索路径中。您需要使用绝对路径加载 DLL，否则行为未定义。为了方便起见，我们可以子类化ctypes.CDLL and ctypes.WinDLL打电话LoadLibraryEx代替LoadLibrary.
import ctypes
from ctypes import wintypes
kernel32 = ctypes.WinDLL('kernel32', use_last_error=True)
def check_bool(result, func, args):
if not result:
raise ctypes.WinError(ctypes.get_last_error())
return args
kernel32.LoadLibraryExW.errcheck = check_bool
kernel32.LoadLibraryExW.restype = wintypes.HMODULE
kernel32.LoadLibraryExW.argtypes = (wintypes.LPCWSTR,
wintypes.HANDLE,
wintypes.DWORD)
class CDLLEx(ctypes.CDLL):
def __init__(self, name, mode=0, handle=None,
use_errno=True, use_last_error=False):
if handle is None:
handle = kernel32.LoadLibraryExW(name, None, mode)
super(CDLLEx, self).__init__(name, mode, handle,
use_errno, use_last_error)
class WinDLLEx(ctypes.WinDLL):
def __init__(self, name, mode=0, handle=None,
use_errno=False, use_last_error=True):
if handle is None:
handle = kernel32.LoadLibraryExW(name, None, mode)
super(WinDLLEx, self).__init__(name, mode, handle,
use_errno, use_last_error)
这是所有可用的LoadLibraryEx flags:
DONT_RESOLVE_DLL_REFERENCES = 0x00000001
LOAD_LIBRARY_AS_DATAFILE = 0x00000002
LOAD_WITH_ALTERED_SEARCH_PATH = 0x00000008
LOAD_IGNORE_CODE_AUTHZ_LEVEL = 0x00000010 # NT 6.1
LOAD_LIBRARY_AS_IMAGE_RESOURCE = 0x00000020 # NT 6.0
LOAD_LIBRARY_AS_DATAFILE_EXCLUSIVE = 0x00000040 # NT 6.0
# These cannot be combined with LOAD_WITH_ALTERED_SEARCH_PATH.
# Install update KB2533623 for NT 6.0 & 6.1.
LOAD_LIBRARY_SEARCH_DLL_LOAD_DIR = 0x00000100
LOAD_LIBRARY_SEARCH_APPLICATION_DIR = 0x00000200
LOAD_LIBRARY_SEARCH_USER_DIRS = 0x00000400
LOAD_LIBRARY_SEARCH_SYSTEM32 = 0x00000800
LOAD_LIBRARY_SEARCH_DEFAULT_DIRS = 0x00001000
例如：
if __name__ == '__main__':
basepath = os.path.dirname(os.path.abspath(__file__))
dllpath = os.path.join(basepath, 'dlls', 'NIDAQmx.dll')
nidaq = CDLLEx(dllpath, LOAD_WITH_ALTERED_SEARCH_PATH)
