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PODynamically attaching a method to an existing Python object generated with swig?
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  1. PODynamically attaching a method to an existing Python object generated with swig?
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    copied!<p>I am working with a Python class, and I don't have write access to its declaration. How can I attach a custom method (such as <strong><code>__str__</code></strong>) to the objects created from that class without modifying the class declaration?</p> <p>EDIT: Thank you for all your answers. I tried them all but they haven't resolved my problem. Here is a minimal example that I hope will clarify the issue. I am using swig to wrap a C++ class, and the purpose is to override the <code>__str__</code> function of <strong>an object</strong> returned by the swig module. I use cmake to build the example:</p> <p><strong>test.py</strong></p> <pre><code>import example ex = example.generate_example(2) def prnt(self): return str(self.x) #How can I replace the __str__ function of object ex with prnt? print ex print prnt(ex) </code></pre> <p><strong>example.hpp</strong></p> <pre><code>struct example { int x; }; example generate_example(int x); </code></pre> <p><strong>example.cpp</strong></p> <pre><code>#include "example.hpp" #include &lt;iostream&gt; example generate_example(int x) { example ex; ex.x = x; return ex; } int main() { example ex = generate_example(2); std::cout &lt;&lt; ex.x &lt;&lt; "\n"; return 1; } </code></pre> <p><strong>example.i</strong></p> <pre><code>%module example %{ #include "example.hpp" %} %include "example.hpp" </code></pre> <p><strong>CMakeLists.txt</strong></p> <pre><code>cmake_minimum_required(VERSION 2.6) find_package(SWIG REQUIRED) include(${SWIG_USE_FILE}) find_package(PythonLibs) include_directories(${PYTHON_INCLUDE_PATH}) include_directories(${CMAKE_CURRENT_SOURCE_DIR}) set_source_files_properties(example.i PROPERTIES CPLUSPLUS ON) swig_add_module(example python example.i example) swig_link_libraries(example ${PYTHON_LIBRARIES}) if(APPLE) set(CMAKE_SHARED_MODULE_CREATE_CXX_FLAGS "${CMAKE_SHARED_MODULE_CREATE_CXX_FLAGS} -flat_namespace") endif(APPLE) </code></pre> <p>To build and run test.py, copy all the files in a directory, and in that directory run</p> <pre><code>cmake . make python test.py </code></pre> <p>This results in the following output:</p> <pre><code>&lt;example.example; proxy of &lt;Swig Object of type 'example *' at 0x10021cc40&gt; &gt; 2 </code></pre> <p>As you can see the swig object has its own <strong>str</strong> function, and that is what I am trying to override. </p>
 

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