<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv=Content-Type content="text/html; charset=us-ascii">
<meta name=Generator content="Microsoft Word 12 (filtered medium)">
<style>
<!--
/* Font Definitions */
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-compose;
font-family:"Calibri","sans-serif";
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;}
@page Section1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.Section1
{page:Section1;}
-->
</style>
<!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang=EN-US link=blue vlink=purple>
<div class=Section1>
<p class=MsoNormal>I am just entering the world of Python embedding and I am
running into a bug I am having a hard time fixing. Please be gentle.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I am creating a small test application in Windows to test
the embedding of the interpreter in order to execute arbitrary Python
statements and print their results, all via a dialog application.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Strings are sent to the interpreter via:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='text-indent:.5in;text-autospace:none'><span
style='font-size:10.0pt;font-family:"Courier New"'>PyRun_String(CString(*pbstrInput),
Py_file_input, _d, _d);<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'>Where _d is my global
dictionary.<o:p></o:p></p>
<p class=MsoNormal style='text-autospace:none'><o:p> </o:p></p>
<p class=MsoNormal style='text-autospace:none'>I would like to capture the
output, so I created a small class to extend Python<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> PyRun_String(<span
style='color:maroon'>"class OutputCatcher:\n"<o:p></o:p></span></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> <span
style='color:maroon'>"\tdef __init__(self):\n"<o:p></o:p></span></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> <span
style='color:maroon'>"\t\tself.data=''\n"<o:p></o:p></span></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> <span
style='color:maroon'>"\tdef write(self, stuff):\n"<o:p></o:p></span></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> <span
style='color:maroon'>"\t\tself.data = stuff\n\n"<o:p></o:p></span></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> <span
style='color:maroon'>"import sys\n"</span><span style='color:green'><o:p></o:p></span></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> <span
style='color:maroon'>"_outcatcher = OutputCatcher()\n"<o:p></o:p></span></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> <span
style='color:maroon'>"sys.stdout = _outcatcher\n"</span>,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'>
Py_file_input, _d, _d);<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal>Using this class, I thought I could access “_outcatcher.data”
to get the last thing written to sys.stdout, and this does seem to work using
the following code:<o:p></o:p></p>
<p class=MsoNormal> <o:p></o:p></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> PyObject* o =
PyDict_GetItemString(_d, <span style='color:maroon'>"_outcatcher"</span>);<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> PyObject* a =
PyObject_GetAttrString(o, <span style='color:maroon'>"data"</span>);<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'> ::MessageBox(NULL,
PyString_AsString(a), _T(<span style='color:maroon'>""</span>),
NULL);<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal>However, it only works twice. On the third try, I get an
access violation trying to access the stdout object (for a print statement).
The pointer appears to be valid, but all of the data has overwritten with
0xDBDBDBDB, with obvious consequences. <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Thanks for any help.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>~Brad Johnson<o:p></o:p></p>
</div>
</body>
</html>