[python-win32] Data Type Conversion in Python Win32 COM

[Mark Hammond]

Pythoncom does its conversions in oleargs.cpp in the source tree.  My guess
is that we are hitting a path causing one of the "*_AsLong" or similar
functions to fail, returning -1, but we don't check that error condition.
However, the best I can tell, the test suite does try and cover these cases
(see win32com\test\testpycomtest.py and search for "ulong").  Also, things
behave differently based on whether typeinfo is available - if it is not,
Python "guesses" about the variant type based on the python type, but if it
is known, python attempts to convert the python value to the requested type.

 

Can you provide any more info, or suggest how testpycomtest could be
modified to demonstrate the problem?

 

Mark

 

From: python-win32-bounces+mhammond=keypoint.com.au at python.org
[mailto:python-win32-bounces+mhammond=keypoint.com.au at python.org] On Behalf
Of Chen
Sent: Friday, 22 February 2008 3:21 AM
To: python-win32 at python.org
Subject: [python-win32] Data Type Conversion in Python Win32 COM

 

Hello,

I have a question regarding to how Data type is being converted into COM
object.

For example, there is a function A in one COM object that requires an
Unsigned 32 bit Integer as a parameter. How could I pass a Long Integer in
python to Function A.

I found that if the parameter is smaller or equal to ( 2^31 -1 ), the
parameter is correctly passed to Function A. Any value that bigger than ( 2
^31 - 1) will be interpreted as 0xFFFFFFFF. Does Python Win32 COM has its
own data conversion if the data type of the passed parameter is different
from the data type of the required parameter. If yes, how python win32 COM
does the conversion?

Thanks


Chen

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