How do i control my led on/off by python application when i am connecting DC jack for power supply not the usb one
assuming you have a UNO or similar, you can have both the USB plugged in and the Jack.
Power will come from the Jack if it's above ~7V and the Serial communication will go through the USB as expected.
if you unplug the Jack, power will be taken from the USB and the communication will still be maintained.
(if you use the USB then there is no reason to power the Arduino from the Jack)
Well first of all you have to get a serial connector from the computer you are running the Python script into the Arduino. The simplest way is through the USB lead which for some reason you don't want to use.
So get a USB to TTL lead and plug it into your computer running Python and connect the lead's TX and RX pins to the Arduino's pins 1 and 2.
But I do think you are missing something here.
@vishudesh, your topic has been moved to a more suitable location on the forum. Installation and Troubleshooting is not for problems with (nor for advise on) your project 
See About the Installation & Troubleshooting category.
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