import re
def full_port_name(portname):
""" Given a port-name (of the form COM7,
COM12, CNCA0, etc.) returns a full
name suitable for opening with the
Serial class.
"""
m = re.match('^COM(d+)$', portname)
if m and int(m.group(1)) < 10:
return portname
return '\.' + portname