What is the cross-platform method of enumerating serial ports in Python (including virtual ports)?

Question

Note: I'm using Python 2.7, and pySerial for serial communications.

I found this article which lists two ways: http://www.zaber.com/wiki/Software/Python#Displaying_a_list_of_available_serial_ports

This method works on Windows and Linux, but sometimes misses virtual ports on Linux:

import serial

def scan():
   # scan for available ports. return a list of tuples (num, name)
   available = []
   for i in range(256):
       try:
           s = serial.Serial(i)
           available.append( (i, s.portstr))
           s.close()
       except serial.SerialException:
           pass
   return available

print "Found ports:"
for n,s in scan(): print "(%d) %s" % (n,s)

And this one that only works on Linux, but includes virtual ports:

import serial, glob

def scan():
   # scan for available ports. return a list of device names.
   return glob.glob('/dev/ttyS*') + glob.glob('/dev/ttyUSB*')

print "Found ports:"
for name in scan(): print name

I suppose I could do platform detection to use the second method (the one that includes virtual ports) when running on Linux, and the first method when running Windows, but what about Mac?

How should I enumerate serial ports (virtual too) regardless of platform?

Edit

I found a few pertinent questions:

I've been doing cross-platform serial stuff for years, and I always hack together the same silly platform detection, globbing, manually tweaked monster every time. I'll be interested to see if you get any nice answers. — detly
Well, I guess that's what it's going to have to be then :(. When I have time I'll test it on Linux and Mac, and see if I can't wrap it up into a library. — Chris Laplante
Give it a couple of days, someone might have a more elegant solution :) — detly
Just thought I'll add it here. bitpim had quite a bit of code for comscan on multiple platforms. Probably useful to get some code out of there to build a cross platform serial port enumerator. bitpim.svn.sourceforge.net/viewvc/bitpim/trunk/bitpim/src/… — Nandeep Mali
@n9986: That looks really promising, thanks! You should make it an answer. — Chris Laplante

Chris Laplante Chris Laplante · Accepted Answer · 2012-07-09T15:39:24

This is what I've been using. It's a mashup of the methods I posted above. I'd still like to see better solutions, though.

# A function that tries to list serial ports on most common platforms
def list_serial_ports():
    system_name = platform.system()
    if system_name == "Windows":
        # Scan for available ports.
        available = []
        for i in range(256):
            try:
                s = serial.Serial(i)
                available.append(i)
                s.close()
            except serial.SerialException:
                pass
        return available
    elif system_name == "Darwin":
        # Mac
        return glob.glob('/dev/tty*') + glob.glob('/dev/cu*')
    else:
        # Assume Linux or something else
        return glob.glob('/dev/ttyS*') + glob.glob('/dev/ttyUSB*')

What is the cross-platform method of enumerating serial ports in Python (including virtual ports)?

4 Answers