I am working on creating a python API for a dll for a daqboard we have
here. I have the documentation for the library, as well as the C, Delphi
and VB api. I have decided to use ctypes for the project, and most is
working out alright. However I have run in to considerable headaches when
dealing with pointers to arrays. The function I am first working with,
requires a pointer to an array of strings that will contain the names of all
the devices installed. Here is a snippet of the code I have so far:
def GetDeviceList():
"""Returns a list of currently configured device names"""
devices = []
count = GetDeviceCount()
countpnt = ct.pointer(ct.c_int(count))
devlist = (ct.c_char_p * count)()
daq.daqGetDeviceList(devlist, countpnt)
for i in devlist:
devices.append(i)
return devices
Using Python 2.6.3 the IDLE goes into an infinite loop of, from what I can
gather, Tkinter errors, and Im unable to kill the command to actually read
all of the errors.
When using Python 3.1.1, I get this error:
Python 3.1.1 (r311:74483, Aug 17 2009, 17:02:12) [MSC v.1500 32 bit (Intel)]
on win32
Type "copyright", "credits" or "license()" for more information.
>>> import daqX
>>> daqX.GetDeviceList()
Traceback (most recent call last):
File "<pyshell#1>", line 1, in <module>
daqX.GetDeviceList()
File "C:\Python31\daqX.py", line 54, in GetDeviceList
for i in devlist:
ValueError: invalid string pointer 0x42716144
>>>
I am really at a loss here, so any insight at all would be great. Something
odd though, is that when I pass just c_char_p instead of an array of
c_char_p, I receive the one device I have installed on this computer, and it
works great. However, when I make an array of just one item, I get these
odd errors.
--
Nathaniel Christopher Hayes
Third Year Mechanical Engineering
Email: nathaniel.ha...@maine.edu
--
http://mail.python.org/mailman/listinfo/python-list
