with open('com1', 'r') as f:

Gabriel Genellina gagsl-py2 at yahoo.com.ar
Fri Apr 3 15:44:09 CEST 2009

En Thu, 02 Apr 2009 20:04:14 -0300, gert <gert.cuykens at gmail.com> escribió:
> On Apr 2, 8:53 pm, Kushal Kumaran <kushal.kuma... at gmail.com> wrote:
>> On Thu, 2 Apr 2009 10:01:02 -0700 (PDT)
>> gert <gert.cuyk... at gmail.com> wrote:

>> > from subprocess import *
>> > check_call(['mode', 'COM1:9600,N,8,1,P'],shell=True)
>> > while True:
>> >     with open('com1', 'r') as f:
>> >         for line in f:
>> >              print('line')
>> > This works very well except for one thing. After a reboot I have to
>> > launch 1 time any windows serial exe application no mater with one,
>> > that just opens an closes the com port, before i can launch this
>> > script. The script keeps on working even after closing and reopening
>> > it, until i reboot the pc. Then again I have to launch one time a
>> > serial.exe and close it again. The exe does not run anything in the
>> > background it just does something in windows python does not do when
>> > it reads from the com port after a fresh reboot.
>> > And i really appreciate it if somebody knew what it was.
>> I don't know why you're getting this behaviour, but have you tried using
>> a python library for accessing the serial port?  
>> Seehttp://pyserial.wiki.sourceforge.net/pySerial.
> I am sorry but I don't think pyserial will work on python3.x and I
> also like to know whats going on before I consider it.

A real Windows program accessing the serial port is likely to use  
SetupComm, SetCommState, and other functions in addition to CreateFile.
See http://msdn.microsoft.com/en-us/library/aa363196(VS.85).aspx

pySerial takes care of all those details, as suggested.

> Maybe its a bug in open() on windows?

open() doesn't care about the file name; it's the OS that interprets  
"com1" as a serial port.

Gabriel Genellina

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