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POHow to create lambda's from Python/C
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copied!<p>We're working on some Python/C-API code, and we've encountered a method that would like to be passed a callback. The method will ship periodic updates to the callback as a form a feedback. As it turns out, we're not that interested in periodic feedback. The only way to disable the method's default feedback mechanism is to pass it some kind of callback.</p> <p>The technique we've employed is to declare a module level function that just returns None, ie:</p> <pre><code>static PyObject* donothing(PyObject* self, PyObject* args) { return Py_None; } </code></pre> <p>But of course, this function also needs to be registered with the modules method table, ie:</p> <pre><code>static PyMethodDef methods[] = { {"donothing", donothing, METH_VARARGS, "do nothing"}, ... {NULL} }; </code></pre> <p>Then, when we go to call the method, we need to grab a reference to this method, ie: <code>PyObject_GetAttrString(module_reference, "donothing").</code></p> <p>All of this feels like we're spending too much time spinning our wheels just to do nothing. Then it ocurred to me..hey, seems like a perfect use for <strong>lambda x: None</strong>. But after spending an hour with the Python/C-API docs, I can't figure out how one create's lambdas.</p> <p>I see there are references to closures on the page <a href="http://docs.python.org/2/c-api/function.html" rel="nofollow">http://docs.python.org/2/c-api/function.html</a>, but I can't sort out the details on how one creates them.</p> <p>Any pointers (or references to RTFM) would be greatly appreciated.</p>

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