Using Virtual Observatory with Python: querying remote astronomical databases

6 pages, 2 figures + python code (tutorial corrected in {\S}4 [remark in red]) - see also: http://goo.gl/mr9wZpThis tutorial is devoted to extending an existing catalogue with data taken elsewhere, either from CDS Vizier or Simbad database. As an example, we used the so-called 'Spectroscopic Survey of Stars in the Solar Neighborhood' (aka. S4N, Allende Prieto et al. 2004) in order to retrieve all objects with available data for the set of fundamental stellar parameters effective temperature, surface gravity and metallicity. Then for each object in this dataset we query Simbad database to retrieve the projected rotational velocity. This combines Vizier and Simbad queries made using Python astroquery module. The tutorial covers remote database access, filtering tables with arbitrary criteria, creating and writing your own tables, and basics of plotting in Python