How to disable/enable usb ports using python

Hey, Im new to python and trying to code a script which should enable/disable usb using winreg. Whats wrong in this code

code:

import winreg
def usbenordis(valu e):
try:
keyval=r"HKEY_L OCAL_MACHINE\SY STEM\CurrentCon trolSet\Service s\UsbStor"
if not os.path.exists( "keyval"):
key = CreateKey(HKEY_ CURRENT_USER,ke yval)
Registrykey= OpenKey(HKEY_CU RRENT_USER, r"HKEY_LOCAL_MA CHINE\SYSTEM\Cu rrentControlSet \Services\UsbSt or", 0,KEY_WRITE)
if value == true:
SetValueEx(Regi strykey,"start" ,0,REG_SZ,4)
print "usb disabled"
elif value == false:
SetValueEx(Regi strykey,"start" ,0,REG_SZ,3)
print "usb enabled"
CloseKey(Regist rykey)
return True
except WindowsError:
return False
def main():
x=usbenordis(tr ue)