Sample of direct communication with virtual game controller using Python. The first file uses PyWin32 and works directly with the Windows API, for older versions of vJoy. The second file uses the DLL of vJoy SDK to command the device.

vjoy.py

from win32file import *
import struct, time

CONST_PPJOY_DEVICE = "\\\\.\\PPJoyIOCTL1"
CONST_LOAD_POSITIONS = 0x910

class vJoy(object):
	def __init__(self):
		self.handle = None
		
	def open(self):
		self.handle = CreateFile( CONST_PPJOY_DEVICE, GENERIC_WRITE | GENERIC_READ, FILE_SHARE_WRITE | FILE_SHARE_READ, None, OPEN_EXISTING, 0, None )
		if self.handle.__class__.__name__ == "PyHANDLE":
			return True
		return False
	def close(self):
		if self.handle.__class__.__name__ == "PyHANDLE":
			self.handle.close()
			return True
		return False
	def generateJoystickPosition(self, 
		wThrottle = 0, wRudder = 0, wAileron = 0, 
		wAxisX = 0, wAxisY = 0, wAxisZ = 0,
		wAxisXRot = 0, wAxisYRot = 0, wAxisZRot = 0,
		wSlider = 0, wDial = 0, wWheel = 0,
		wAxisVX = 0, wAxisVY = 0, wAxisVZ = 0,
		wAxisVBRX = 0, wAxisVBRY = 0, wAxisVBRZ = 0,
		lButtons = 0, bHats = 0):
		"""
		typedef struct _JOYSTICK_POSITION
		{
			LONG	wThrottle;
			LONG	wRudder;
			LONG	wAileron;
			LONG	wAxisX;
			LONG	wAxisY;
			LONG	wAxisZ;
			LONG	wAxisXRot;
			LONG	wAxisYRot;
			LONG	wAxisZRot;
			LONG	wSlider;
			LONG	wDial;
			LONG	wWheel;
			LONG	wAxisVX;
			LONG	wAxisVY;
			LONG	wAxisVZ;
			LONG	wAxisVBRX;
			LONG	wAxisVBRY;
			LONG	wAxisVBRZ;
			LONG	lButtons;	// 32 buttons: 0x00000001 means button1 is pressed, 0x80000000 -> button32 is pressed
			UCHAR	bHats;		// Lower 4 bits: HAT switch
		} JOYSTICK_POSITION, *PJOYSTICK_POSITION;
		"""
		joyPosFormat = "lllllllllllllllllllB"
		pos = struct.pack( joyPosFormat, wThrottle, wRudder, wAileron, wAxisX, wAxisY, wAxisZ, wAxisXRot, wAxisYRot, wAxisZRot, wSlider, wDial, wWheel, wAxisVX, wAxisVY, wAxisVZ, wAxisVBRX, wAxisVBRY, wAxisVBRZ, lButtons, bHats )
		return pos
	def update(self, joystickPosition):
		if self.handle.__class__.__name__ == "PyHANDLE":
			DeviceIoControl(self.handle, CONST_LOAD_POSITIONS, joystickPosition, 0 )
			return True
		return False
	def sendButtons( self, bState ):
		joyPosition = self.generateJoystickPosition( lButtons = bState )
		return self.update( joyPosition )

vj = vJoy()

def test():
	vj.open()
	btn = 1
	time.sleep(2)
	for i in range(0,10,1):
		vj.sendButtons( btn << i )
		time.sleep( 1 )
	vj.sendButtons(0)
	vj.close()

vjoy2.py

import ctypes
import struct, time

CONST_DLL_VJOY = "C:\\Program Files\\vJoy\\x64\\vJoyInterface.dll"

class vJoy(object):
    def __init__(self, reference = 1):
        self.handle = None
        self.dll = ctypes.CDLL( CONST_DLL_VJOY )
        self.reference = reference
        self.acquired = False
        
    def open(self):
        if self.dll.AcquireVJD( self.reference ):
            self.acquired = True
            return True
        return False
    def close(self):
        if self.dll.RelinquishVJD( self.reference ):
            self.acquired = False
            return True
        return False
    def generateJoystickPosition(self, 
        wThrottle = 0, wRudder = 0, wAileron = 0, 
        wAxisX = 0, wAxisY = 0, wAxisZ = 0,
        wAxisXRot = 0, wAxisYRot = 0, wAxisZRot = 0,
        wSlider = 0, wDial = 0, wWheel = 0,
        wAxisVX = 0, wAxisVY = 0, wAxisVZ = 0,
        wAxisVBRX = 0, wAxisVBRY = 0, wAxisVBRZ = 0,
        lButtons = 0, bHats = 0, bHatsEx1 = 0, bHatsEx2 = 0, bHatsEx3 = 0):
        """
        typedef struct _JOYSTICK_POSITION
        {
            BYTE    bDevice; // Index of device. 1-based
            LONG    wThrottle;
            LONG    wRudder;
            LONG    wAileron;
            LONG    wAxisX;
            LONG    wAxisY;
            LONG    wAxisZ;
            LONG    wAxisXRot;
            LONG    wAxisYRot;
            LONG    wAxisZRot;
            LONG    wSlider;
            LONG    wDial;
            LONG    wWheel;
            LONG    wAxisVX;
            LONG    wAxisVY;
            LONG    wAxisVZ;
            LONG    wAxisVBRX;
            LONG    wAxisVBRY;
            LONG    wAxisVBRZ;
            LONG    lButtons;   // 32 buttons: 0x00000001 means button1 is pressed, 0x80000000 -> button32 is pressed
            DWORD   bHats;      // Lower 4 bits: HAT switch or 16-bit of continuous HAT switch
                        DWORD   bHatsEx1;   // 16-bit of continuous HAT switch
                        DWORD   bHatsEx2;   // 16-bit of continuous HAT switch
                        DWORD   bHatsEx3;   // 16-bit of continuous HAT switch
        } JOYSTICK_POSITION, *PJOYSTICK_POSITION;
        """
        joyPosFormat = "BlllllllllllllllllllIIII"
        pos = struct.pack( joyPosFormat, self.reference, wThrottle, wRudder,
                                   wAileron, wAxisX, wAxisY, wAxisZ, wAxisXRot, wAxisYRot,
                                   wAxisZRot, wSlider, wDial, wWheel, wAxisVX, wAxisVY, wAxisVZ,
                                   wAxisVBRX, wAxisVBRY, wAxisVBRZ, lButtons, bHats, bHatsEx1, bHatsEx2, bHatsEx3 )
        return pos
    def update(self, joystickPosition):
        if self.dll.UpdateVJD( self.reference, joystickPosition ):
            return True
        return False
    #Not working, send buttons one by one
    def sendButtons( self, bState ):
        joyPosition = self.generateJoystickPosition( lButtons = bState )
        return self.update( joyPosition )
    def setButton( self, index, state ):
        if self.dll.SetBtn( state, self.reference, index ):
            return True
        return False
                

vj = vJoy()

def test():
    vj.open()
    btn = 1
    time.sleep(2)
    for i in range(0,10,1):
        vj.sendButtons( btn << i )
        time.sleep( 1 )
    vj.sendButtons(0)
    vj.close()

Based on vJoyDemo project @ http://vjoystick.sourceforge.net/site/index.php/79-dev-and-technical-issues/76-feeder-app?showall=&start=1