<div dir="ltr">I believe it's possible, yes, but it will be challenging. I'm not aware of anybody else doing this.<div><br></div><div>In <a href="https://github.com/OSGeo/gdal/blob/trunk/gdal/swig/python/extensions/gdal_wrap.cpp">https://github.com/OSGeo/gdal/blob/trunk/gdal/swig/python/extensions/gdal_wrap.cpp</a> you can see examples of C++ functions that access the GDAL objects referenced by Python objects. This isn't a stable public API by any means, and therefore I hesitate to recommend it. Maybe Even would be able to comment more on how much support there is for the SWIG-generated C++ Python classes.</div><div><br></div><div>I presume you've already tried writing "<span style="color:rgb(0,0,0);font-family:Tahoma;font-size:13.3333px">_my_module" in Python and found it to be too slow? </span></div><div><span style="color:rgb(0,0,0);font-family:Tahoma;font-size:13.3333px"><br></span></div><div>Good luck!</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Nov 27, 2017 at 9:34 AM, Shawn Gong <span dir="ltr"><<a href="mailto:SGONG@mdacorporation.com" target="_blank">SGONG@mdacorporation.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<div class="m_1828817089082271248PlainText"><font face="Tahoma">Thank you Sean.</font></div>
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<p><font size="2"><font face="Tahoma">What I want to do is to compile C/C++ code into "_my_c_module.pyd" and then to be called by Python. The Python code passes an argument to C/C++.</font></font></p>
<p><font size="2"><font face="Tahoma">I did previously by passing a file name (str) or a numpy array as argument to C/C++, and it is all good.
</font></font></p>
<p>This time I want to pass a gdal dataset as an argument:</p>
<p> </p>
<p>in Python:</p>
<p> from osgeo import gdal</p>
<p> import _my_c_module</p>
<p> ds=gdal.Open('my_filename"<wbr>)</p>
<p> result = _my_c_module.function1(ds)</p>
<p><font size="2"><font face="Tahoma"> </font></font></p>
<p class="m_1828817089082271248PlainText">is this possible? If yes, how?</p>
<p class="m_1828817089082271248PlainText"> </p>
<p class="m_1828817089082271248PlainText"><br>
Shawn<br>
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<div id="m_1828817089082271248divRpF956507" style="DIRECTION:ltr"><font color="#000000" size="2" face="Tahoma"><b>From:</b> Sean Gillies [<a href="mailto:sean@mapbox.com" target="_blank">sean@mapbox.com</a>]<br>
<b>Sent:</b> November-27-17 11:09 AM<br>
<b>To:</b> Shawn Gong<br>
<b>Cc:</b> <a href="mailto:gdal-dev@lists.osgeo.org" target="_blank">gdal-dev@lists.osgeo.org</a><br>
<b>Subject:</b> Re: [gdal-dev] pass gdal dataset as an argument from Python to C<br>
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<div dir="ltr">Shawn,
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<div>PyObject and GDALDatasetH are incompatible types and you can't pass the former to a function that expects the latter. I'm surprised your program can compile with these incompatible types.</div>
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<div>Do you mean for your module to extend GDAL's Python bindings? If you look inside the C code of GDAL's Python bindings you may be able to see how to get the GDALDatasetH associated with a Python dataset object.</div>
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<div>Hope this helps,</div>
<div><br>
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<div class="gmail_extra"><br>
<div class="gmail_quote">On Thu, Nov 23, 2017 at 1:25 PM, Shawn Gong <span dir="ltr">
<<a href="mailto:SGONG@mdacorporation.com" target="_blank">SGONG@mdacorporation.com</a>></span> wrote:<br>
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<p>Hi list,</p>
<p> </p>
<p>Has anyone done this before?</p>
<p>I try to pass a gdal dataset as an argument from Python to C.</p>
<p> </p>
<p>in my C code, I have</p>
<p>PyObject* py_my_func(PyObject *self, PyObject *args)<br>
{</p>
<p> PyObject *poDataset;</p>
<p> </p>
<p> if(!PyArg_ParseTuple(args, "Odd", &poDataset, &a1, &a2))<br>
{<br>
return NULL;<br>
}</p>
<p> </p>
<p> my_func(poDataset, a1, a2);<br>
}</p>
<p> </p>
<p>void my_func(GDALDatasetH hDataset, double a1, double a2)</p>
<p>{</p>
<p>}</p>
<p> </p>
<p>Python crashed and hDataset was NULL</p>
<p>Is it possible to do or I did something wrong?</p>
<p> </p>
<p>BTW, I have passed either a filename or a gdal array as an argument from Python to C, with success.</p>
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<div class="m_1828817089082271248m_3308011925270217570PlainText"><font face="Tahoma">Thanks,<br>
Shawn<br>
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-- <br>
<div class="m_1828817089082271248gmail_signature">
<div dir="ltr">Sean Gillies</div>
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</blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr">Sean Gillies</div></div>
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