I dont know how to send and integer by serial port from raspberry to arduino

I am trying to connect my raspberry pi with an arduino mega via usb. I did the connection and I can send an integer but only if i put the number by keyboard here is the code:

import serial
import time
arduino=serial.Serial('/dev/ttyUSB0',baudrate=9600, timeout = 3.0)

var = raw_input("Introducir un Comando: ")

It works

but if I want to send a varible integer like

var=1 it appears an error saying that the port is close, only making this change. I tried using var =1, var ='1' var ="1" but nothing.

Can anyone help me? thanks and sorry for my bad english.


My friends helped me. The way to send is:

after open the port wait with the time library 1 second.

import time

and then the way to send it is:


and we send a number 3. Thanks to everyone.

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