send-file.py

#!/usr/bin/env python
import serial
import sys
from xmodem import XMODEM

# Setup: 
#   pip install pyserial
#   pip install xmodem


ser = serial.Serial('/dev/ttyUSB0', timeout=0) # or whatever port you need

def getc(size, timeout=1):
    return ser.read(size) or None

def putc(data, timeout=1):
    return ser.write(data)  # note that this ignores the timeout

modem = XMODEM(getc, putc)

with open(sys.argv[1], "rb") as f:
    modem.send(f)