.. _excel:


Using Excel addins (third party, on Windows)
========================================================

Many third-party libraries are only delivered as Excel add-ins.
While using Excel is exactly the opposite of what we advocate, sometimes you may have no choice,
for example if you have to use 3rd party Excel add-ins.

The simplest way to add such libraries to our framework  
Python's *Application.Run*.

The only problem with this approach is that it is not fully automated.
An open Excel session with the addin loaded is required when running
Python scripts containing *Application.Run*.


.. contents::
   :depth: 3
   :local:
   :backlinks: entry


Excel add-in
--------------

Implement the functions we defined in :ref:`square`, in an Excel add-in.

:: 

  Function mySquare(a As Double) As Double
  mySquare = a * a
  End Function

  Function myCube(a As Double) As Double
  myCube = a * a * a
  End Function

Save the add-in as "addinTest.xlam".


Run the Excel add-in
----------------------------------------------

Click on the file "addinTest.xlam" you just saved.
Then paste the code below in an interactive Python session.
This will produce the plot below.

::

   import win32com.client
   xl = win32com.client.Dispatch("Excel.Application")
   from matplotlib import pyplot as plt
   N = 10
   x = [i/N for i in range(0,N+1)]
   y = [xl.Application.Run('mySquare', t) for t in x]
   z = [xl.Application.Run('myCube', t) for t in x]
   plt.plot(x, y, 'r')
   plt.plot(x, y, '*r', label='square')
   plt.plot(x, z, 'b')
   plt.plot(x, z, 'ob', label='cube')
   plt.xlabel('x')
   plt.ylabel('values')
   plt.title('Plots of $y = x^2$ and $z = x^3$')
   plt.legend(loc='upper left')
   
   

.. image:: squareCube.png
   :scale: 80%