How Can I Use DLL Files in Python Without C Wrappers?

Using DLL Files in Python without C Wrappers

Utilizing DLL files within Python can be achieved seamlessly without resorting to additional C wrappers. One highly recommended and straightforward approach is employing ctypes.

Introducing ctypes

ctypes provides a native Python module that facilitates interaction with C-compatible libraries. It supplies data types analogous to C (e.g., int, char, void*) and enables passing parameters by value or reference. Additionally, it can handle the return of specific data types.

Example Usage

Consider the following example, based on actual code (Python 2.5):

<code class="python">import ctypes

# Load the DLL.
hllDll = ctypes.WinDLL("c:\PComm\ehlapi32.dll")

# Function prototype and parameters.
hllApiProto = ctypes.WINFUNCTYPE(ctypes.c_int, ctypes.c_void_p,
                                ctypes.c_void_p, ctypes.c_void_p, ctypes.c_void_p)
hllApiParams = ((1, "p1", 0), (1, "p2", 0), (1, "p3", 0), (1, "p4", 0))

# Function mapping.
hllApi = hllApiProto(("HLLAPI", hllDll), hllApiParams)

# Function call.
p1 = ctypes.c_int(1)
p2 = ctypes.c_char_p(sessionVar)
p3 = ctypes.c_int(1)
p4 = ctypes.c_int(0)
hllApi(ctypes.byref(p1), p2, ctypes.byref(p3), ctypes.byref(p4))</code>

In this example, the HLL API is employed and parameters are passed by value or reference (as per HLLAPI specifications). The function is mapped to a Python name (hllApi) and invoked with the necessary variables.

Conclusion

By utilizing ctypes and following the illustrated approach, developers can seamlessly interact with DLL files without the need for external C code. This empowers them to leverage the capabilities of these libraries directly from within their Python scripts.

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