Error on Python serial import

Question

When I try to import the serial I get the following error:

Traceback (most recent call last):
  File "C:Documents and Settingseduardo.pereiraworkspacethgspeaktst.py", line 7, in <module>
    import serial
  File "C:Python27libsite-packagesserial__init__.py", line 27, in <module>
    from serial.serialwin32 import Serial
  File "C:Python27libsite-packagesserialserialwin32.py", line 15, in <module>
    from serial import win32
  File "C:Python27libsite-packagesserialwin32.py", line 182, in <module>
    CancelIoEx = _stdcall_libraries['kernel32'].CancelIoEx
  File "C:Python27libctypes__init__.py", line 375, in __getattr__
    func = self.__getitem__(name)
  File "C:Python27libctypes__init__.py", line 380, in __getitem__
    func = self._FuncPtr((name_or_ordinal, self))
AttributeError: function 'CancelIoEx' not found

I have installed the latest version of pySerial, Python 2.7 runing on a WinXP laptop. Tried everywhere and found no similar problem. Is there any solution for that?
Thanks in advance…

Asked By: Hagah

||

Source

Answer 1

The version of pySerial that you’re using is trying to call a function that’s only available in Windows Vista, whereas you’re running Windows XP.

It might be worth experimenting with using an older version of pySerial.

The code in question was added to pySerial on 3 May 2016, so a version just prior to that might be a good start.

Answered By: NPE

Answer 2

Older versions seem unavailable. But, this worked for me (assuming nanpy version 3.1.1):

open file libsite-packagesserialserialwin32.py
delete methods _cancel_overlapped_io(), cancel_read(), cancel_write() in lines 436-455 nearly at the botton of the file
change method _close() als follows:

(Python)

def _close(self):
    """internal close port helper"""
    if self._port_handle is not None:
        # Restore original timeout values:
        win32.SetCommTimeouts(self._port_handle, self._orgTimeouts)
        # Close COM-Port:
        if self._overlapped_read is not None:
            win32.CloseHandle(self._overlapped_read.hEvent)
            self._overlapped_read = None
        if self._overlapped_write is not None:
            win32.CloseHandle(self._overlapped_write.hEvent)
            self._overlapped_write = None
        win32.CloseHandle(self._port_handle)
        self._port_handle = None

Additionally, create a non-default serial connection when starting the communication, otherwise you’ll be bound to some linux device:

a = ArduinoApi(SerialManager("COM5:"))

for i in range(10):
    a.pinMode(13, a.OUTPUT)
    a.digitalWrite(13, a.HIGH)
    # etc.

Answered By: user508402

Answer 3

And in serialwin32.py comments

#CancelIoEx = _stdcall_libraries['kernel32'].CancelIoEx
#CancelIoEx.restype = BOOL
#CancelIoEx.argtypes = [HANDLE, LPOVERLAPPED]

Answered By: Vladimir Anufriev

Answer 4

There is no obvious reason why CancelIO was replaced with the cross-thread version CancelIOex, which allows code in one thread to cancel IO in another thread. Certainly cpython 2.x is single threaded.

To get pySerial to run on python 2.7 on Win2K, I just changed CancelIOex in serial back to CancelIO.

Answered By: david

Error on Python serial import

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