ctypes.CDLL(dll)

The `ctypes.CDLL(dll)` function creates a ctypes object representing a dynamic link library (DLL) on Windows or a shared object (SO) on Unix-like systems. The `dll` argument is a string specifying the name or path of the DLL/SO file to be loaded.

Once the ctypes object is created, you can call functions exported by the DLL/SO using the object's attributes. For example, if the DLL/SO contains a function named `my_function` that takes an integer argument and returns a float, you can call it like this:

my_dll = ctypes.CDLL('my_dll.so')  # load the shared object
result = my_dll.my_function(42)    # call the function with argument 42

The `result` variable will contain the float value returned by `my_function`. Note that you need to know the function's argument types and return type in order to call it correctly. You can specify these types using the `argtypes` and `restype` attributes of the function object.