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POcython wrapping of base and derived class
 

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  1. POcython wrapping of base and derived class
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    <p>I am trying to wrap C++ Base and Derived classes and Base is an abstract class. (I have editted this to make this example SSCCE). The Base class defines the interface, I donot like to repeat them in the Derived Python class (not sure is it possible). But I do not know how to tell Cython, Derived is derived from Base. I have tried several ways, but did not succeed.</p> <pre><code>#include &lt;string&gt; class Base { std::string name_; public: Base (const std::string&amp; name): name_(name) {} std::string name() const { return name_; } void setName(const std::string&amp; name) { name_ = name; } virtual double length() const = 0; virtual ~Base() {} }; class Derived: public Base { double len_; public: Derived(const std::string&amp; name, double len) : Base(name), len_(len){ } virtual double length() const { return len_; } void setLength(double len) { len_ = len; } }; </code></pre> <p>I am trying to use Cython wrap these two classes:</p> <pre><code>from libcpp.string cimport string cdef extern from "base.h": cdef cppclass c_Base "Base": string name_ string name() void setName(const string&amp; name) cdef extern from "base.h": ctypedef struct c_Derived "Derived": double len_ double length() void setLength(double v) c_Derived *new_Derived "new Derived" (const string&amp; name, double len) void del_Derived "delete" (c_Derived *p) from tlib cimport c_Derived cdef class Base: cdef c_Base *thisptr def __cinit__(self, const string&amp; name): pass property name: def __get__(self): return self.thisptr.name() def __set__(self, const string&amp; v): self.thisptr.setName(v) cdef class Derived: cdef c_Derived *thisptr # hold a C++ instance which we're wrapping def __cinit__(self, const string&amp; name, double len): self.thisptr = new_Derived(name, len) def __dealloc__(self): del_Derived(self.thisptr) property length: def __get__(self): return self.thisptr.length() def __set__(self, double v): self.thisptr.setLength(v) </code></pre> <p>The setup.py is like this:</p> <pre><code>from distutils.core import setup from distutils.extension import Extension from Cython.Distutils import build_ext setup( name = 'pytlib', ext_modules=[ Extension("tlib", sources=["tlib.pyx"], include_dirs=["."], language="c++"), ], cmdclass = {'build_ext': build_ext}, ) </code></pre>
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    1. USForest Yang
    1. USForest Yang
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    1. COShouldn't `Base::length()` be `virtual`?
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      1. POcython wrapping of base and derived class
      1. USuser2093113
    2. COWhy do you actually need `Base` exposed to Python anyway?
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      1. POcython wrapping of base and derived class
      1. USabarnert
    3. COMeanwhile… there are obvious errors in both the C++ code and the Cython code that probably aren't relevant to your problem, but prevent us from debugging your actual problem. Can you give us a [SSCCE](http://sscce.org) that actually demonstrates your error, instead of failing before we can even get there?
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      1. POcython wrapping of base and derived class
      1. USabarnert
 

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