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			\chapter{Python interface\index{Python}\label{sect:python}}

			Akantu as a python interface which allows to implement a finite
			element case entirely in the Python language. The interface is
			currently in \textcolor{red}{beta} version and bugs (including memory
			leaks) can be expected.

			The philosophy of the python wrappers is that it should follow, as
			much as possible, the C++ interface. This is made possible thanks to
			the \href{SWIG}{} software which can port C++ interfaces to Python.
			However, the possibilities of the Python language have some
			restrictions which do not allow the concept of template. For this
			reason the templated classes and methods are currently hardly
			supported in the Akantu Python interface (some are, but without any
			warranty that the interface shall not change in a near future).

			In order to use the python interface you want to import the
			\code{akantu} module which is possibly located in directory where you
			built or where you installed \akantu. The easiest way is to source
			the file \code{akantu\_environement.sh} in your terminal environment:

			\begin{command}
			source AKANTU_BUILD_DIR/akantu_environement.sh
			\end{command}

			or for an installed akantu version:

			\begin{command}
			source AKANTU_INSTALL_DIR/share/akantuVERSION/akantu_environement.sh
			\end{command}

			Then, you can create a Python script, like \code{script.py} which
			starts with:

			\begin{python}
			import akantu
			\end{python}

			Then, you can write the initialization sequence just like for the C++
			case:

			\begin{python}
			akantu.initialize('materials.dat') spatial_dimension = 2

			mesh = akantu.Mesh(spatial_dimension) mesh.read('mesh.msh')
			model = akantu.SolidMechanicsModel(mesh)
			model.initFull(akantu.SolidMechanicsModelOptions(akantu._static))
			\end{python}
			Then for the dumpers declaration:
			\begin{python}
			model.setBaseName("example") model.addDumpFieldVector("displacement")
			model.addDumpFieldVector("force") model.addDumpField("boundary")
			model.addDumpField("strain") model.addDumpField("stress")
			model.addDumpField("blocked_dofs")
			\end{python}

			The \akantu arrays can be retrieved at all time. For convenience there
			is an automatic trans-typing operator which allows to use \akantu
			Array, Vectors and Matrix as mere \textbf{Numpy}s.

			\begin{python}
			displacement = model.getDisplacement()
			\end{python}

			There is no copy made and the \textbf{Numpy} vectors are wrapped
			around \akantu's memory pool.

			\begin{python}
			displacement[:,:] = 1.
			displacement[0,1] = 10.
			\end{python}

			Also to assign an entire vector to another the '[]' operator must be
			used:

			\begin{python}
			result = numpy.linspace(0.,1.,100)

			# This works
			displacement[:] = result[:]
			# This does not
			displacement = result
			\end{python}

			Then you can solve the problem for instance with:
			\begin{python}
			model.solveStaticDisplacement(1e-10,2);
			\end{python}
			And dump to Paraview:
			\begin{python}
			model.dump()
			\end{python}

			Do not forget to finalize at the end of the script:
			\begin{python}
			akantu.finalize()
			\end{python}

			Finally the python script can be launched with:
			\begin{command}
			python ./script.py
			\end{command}

			\vspace{1cm}

			\textcolor{red}{Warning!} : We recall once more that the Python
			interface is in \textbf{beta} state and is provided only for its nice
			services: it avoids recompilation of akantu when coding the main function.
			Several preliminary examples are provided
			in the \code{examples} directory where it is described how to specify
			boundary conditions and also constitutive behavior.

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