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diff --git a/Doc/FAQ.html b/Doc/FAQ.html new file mode 100644 index 000000000..ad09c262c --- /dev/null +++ b/Doc/FAQ.html @@ -0,0 +1,77 @@ +<!DOCTYPE doctype PUBLIC "-//w3c//dtd html 4.0 transitional//en"> +<html><head> + <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> + <meta name="GENERATOR" content="Mozilla/4.51 (Macintosh; I; PPC) [Netscape]"><title>FAQ.html</title></head> + +<body> + <center> <h1> <hr width="100%">Pyrex FAQ +<hr width="100%"></h1> + </center> + <h2> Contents</h2> + <ul> + <li> <b><a href="#CallCAPI">How do I call Python/C API routines?</a></b></li> + <li> <b><a href="#NullBytes">How do I convert a C string containing null + bytes to a Python string?</a></b></li> + <li> <b><a href="#NumericAccess">How do I access the data inside a Numeric + array object?</a></b></li> + <li><b><a href="#Rhubarb">Pyrex says my extension type object has no attribute +'rhubarb', but I know it does. What gives?</a></b></li><li><a style="font-weight: bold;" href="#Quack">Python says my extension type has no method called 'quack', but I know it does. What gives?</a><br> + </li> + + </ul> + <hr width="100%"> <h2> <a name="CallCAPI"></a>How do I call Python/C API routines?</h2> + Declare them as C functions inside a <tt>cdef extern from</tt> block. +Use the type name <tt>object</tt> for any parameters and return types which +are Python object references. Don't use the word <tt>const</tt> anywhere. +Here is an example which defines and uses the <tt>PyString_FromStringAndSize</tt> routine: +<blockquote><tt>cdef extern from "Python.h":</tt> <br> + <tt> object PyString_FromStringAndSize(char *, int)</tt> <p><tt>cdef char buf[42]</tt> <br> + <tt>my_string = PyString_FromStringAndSize(buf, 42)</tt></p> + </blockquote> + <h2> <a name="NullBytes"></a>How do I convert a C string containing null +bytes to a Python string?</h2> + Put in a declaration for the <tt>PyString_FromStringAndSize</tt> API routine + and use that<tt>.</tt> See <a href="#CallCAPI">How do I call Python/C API + routines?</a> <h2> <a name="NumericAccess"></a>How do I access the data inside a Numeric + array object?</h2> + Use a <tt>cdef extern from</tt> block to include the Numeric header file + and declare the array object as an external extension type. The following + code illustrates how to do this: +<blockquote><tt>cdef extern from "Numeric/arrayobject.h":</tt> <p><tt> struct PyArray_Descr:</tt> <br> + <tt> int type_num, elsize</tt> <br> + <tt> char type</tt> </p> + <p><tt> ctypedef class Numeric.ArrayType [object PyArrayObject]</tt><tt>:</tt> <br> + <tt> cdef char *data</tt> <br> + <tt> cdef int nd</tt> <br> + <tt> cdef int *dimensions, +*strides</tt> <br> + <tt> cdef object base</tt> + <br> + <tt> cdef PyArray_Descr *descr</tt> <br> + <tt> cdef int flags<br> + </tt></p> +</blockquote> +<p>For more information about external extension types, see the <a href="extension_types.html#ExternalExtTypes">"External Extension Types"</a> +section of the <a href="extension_types.html">"Extension Types"</a> documentation +page.<br> +<tt> </tt> </p> + <h2><a name="Rhubarb"></a>Pyrex says my extension type object has no attribute +'rhubarb', but I know it does. What gives?</h2> +You're probably trying to access it through a reference which Pyrex thinks +is a generic Python object. You need to tell Pyrex that it's a reference +to your extension type by means of a declaration,<br> +for example,<br> +<blockquote><tt>cdef class Vegetables:</tt><br> + <tt> cdef int rhubarb</tt><br> + <br> + <tt>...</tt><br> + <tt>cdef Vegetables veg</tt><br> + <tt>veg.rhubarb = 42</tt><br> +</blockquote> +Also see the <a href="extension_types.html#ExtTypeAttrs">"Attributes"</a> +section of the <a href="extension_types.html">"Extension +Types"</a> documentation page.<br> +<h2><a name="Quack"></a>Python says my extension type has no method called 'quack', but I know it does. What gives?</h2> +You may have declared the method using <span style="font-family: monospace;">cdef</span> instead of <span style="font-family: monospace;">def</span>. Only functions and methods declared with <span style="font-family: monospace;">def</span> are callable from Python code.<br> +--- +</body></html>
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