Using Serial on Python / Win7

I am trying to interface with a serial WWAN modem (for diagnostics /signal strength measurement purposes). This is via the onboard COM1 (115200-8-n-1) on my desktop, the connection works via PuTTY. I can script the AT commands using Python, but I am having a tough time getting it to open the serial port .

I have installed Python 2.7.1 and PySerial according to instructions. I am the local administrator of my machine and have run Python with and without admin privileges, but I get the following when I try to open the port:

Python 2.7.1 (r271:86832, Nov 27 2010, 17:19:03) [MSC v.1500 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import serial
>>> s = serial.Serial(
...     port='COM1',
...     baudrate=115200
... )
>>> s.open()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Python27\lib\site-packages\serial\serialwin32.py", line 56, in open
raise SerialException("could not open port %s: %s" % (self.portstr, ctypes.W
inError()))
serial.serialutil.SerialException: could not open port COM1: [Error 5] Access is
 denied.

It is my understanding that 8-N-1 is the default, and even when I try to set them manually it throws the same exception.

Can anyone offer advice? Thanks in advance.

NPE

You don't need to call open. The constructor already does that, and on Windows whoever opens a COM port has exclusive access to it until they close it.

As to the second problem, take a look at How can I fix "[Error 6] The handle is invalid." with PySerial

oyildirim

Here is what I do to eliminate Access Denied Error: