GILDAS-Python binding

Transcription

1 GILDAS-Python binding Using Python from GILDAS, and vice-versa Sébastien BARDEAU, IRAM Grenoble MPIfR, 23-mar-2010

2 A kernel: SIC: Sympathetic Interpreter of Commands GreG: Grenoble Graphic The GILDAS software GILDAS is a collection of state-of-the-art softwares oriented toward (sub-)millimeter radioastronomical applications (either single-dish or interferometer). It is daily used to reduce all data acquired with the IRAM 30M telescope and Plateau de Bure Interferometer PDBI (except VLBI observations). GILDAS is easily extensible. GILDAS is written in Fortran-90, with a few parts in C/C++ (mainly keyboard interaction, plotting, widgets). Dedicated programs: ASTRO: ephemeris and observation preparation CLASS: single-dish spectra OTFCAL: calibration of 30M On- The-Fly data CLIC: calibration of the PdBI 23/03/2010 GILDAS Python binding 2 MAPPING: aperture synthesis and deconvolution...

3 Gildas-Python binding: why? Today: Provide Python functionalities to GILDAS users Provide G ILDAS modules to Python users Allow GILDAS to be used simultaneously/interactively with other Pythonported softwares. Tomorrow: ALMA CASA (Common Astronomy Software Applications) is a packaging of the former AIPS++ through a (i)python scripting interface, binded with the Alma Common Software: Prepare users to Python and CASA Prepare a bridge between GILDAS and CASA 23/03/2010 GILDAS Python binding 3

4 Python: developed since 1990 by Guido von Rossum (a Monty Python fan), written in C. current (parallel) releases are Python (25-oct-2009) and (17-aug-2009). interpreted, interactive, object-oriented, extensible programming language. Syntax: Python (like C) is case-sensitive. Python uses indentation as block delimiters (no begin/end, or {}): 1 or more spaces, and always the same number for the same block. * % or $ are forbidden in identifiers (variable names).. (dot) has a special meaning (objects attributes or methods). * (see usingpython.py) Providing new features to python: Built-in modules * (see usingpython.py) External modules: Python developers community provides a large set of packages (modules) for many purposes. Installation: retrieve the module archive, expand it anywhere, setup.py script uses distutils module * (re)define your PYTHONPATH environment variable for non-standard installation. When installed, just import the module into Python. shell> python setup.py build shell> python setup.py install 23/03/2010 GILDAS Python binding 4

5 Arrays in Arrays in Python: Numeric / Numpy / Numarray modules array handling is inefficient in Python * elements can be any kind of Python object: memory and CPU consuming Numeric or Numpy provide a better handling * only values are stored, single or double precision Numeric: original module but not supported anymore. Numarray (STSCI): based on Numeric but obsolescent NumPy (SciPy): based on Numeric and actively supported, partly merged into Python 3.0 Multidimensional-array arrangement in memory: C (and thus Python) uses row-major order (last dimension is contiguous in memory), and indices run from 0. Fortran (and thus GILDAS) uses columnmajor order (first dimension is contiguous in memory), and indices run from 1. (see usingpython.py) 23/03/2010 GILDAS Python binding 5

6 Requirements Machine / OS: 32 or 64 bits Any Linux supported by GILDAS, Mac OSX. Python: Versions 2.4, 2.5, 2.6 (binaries + headers) Versions 3.* not (yet) supported Array module: Numpy up to latest Or latest Numeric 24.* but support obsolescent 23/03/2010 GILDAS Python binding 6

7 1: Using Python from GILDAS 'SIC\PYTHON' command: First call launches Python interpreter in background No arguments jumps to Python prompt * One python file name as argument executes it * Any other string is sent to Python interpreter * Using Python functions: Search in Python main name space for unknown functions called from SIC * Can accept a variable number of arguments * (see usingpygildas.sic, bessel.greg) (see usingpygildas.sic, onefile.py) 23/03/2010 GILDAS Python binding 7

8 2: Using GILDAS from Python Python modules: pysic and other modules launch the process in background provide useful functions * import variables into the Gildas dictionary. Dynamic definition and deletion. * (see usingpygildas.py) Import naming rules: Names are lowercased, and forbidden characters are converted: SIC ABC ABC%DEF Python abc abc.def Names can not overwrite Python commands ('import', 'def', 'del',...) or built-in objects ('range', 'file', 'type',...) Sharing variables: GILDAS process owns the allocated memory area Numpy arrays point to the same memory area (read and write). 23/03/2010 GILDAS Python binding 8

9 Demos Demos Import FITS file into GILDAS A GreG procedure (from GreG) A Python script (from python) Crossed call (see importfits.greg) (see importfits.py) Import a VO table into GILDAS (see testvotable.greg, testvotable.py) Use another Python-ported software (Miriad) (see gmiriad.map) Miriad is a radio interferometry data reduction package of particular interest to users of the Australia Telescope Compact Array (ATCA). CLASS/Weeds (see J.Pety talk): An extension of Class at user level (i.e. using only class procedures and python scripts). (see gildas doc and sources) 23/03/2010 GILDAS Python binding 9

10 Summary Call Python from GILDAS: 'PYTHON' command SIC> PYTHON Command-line Python arithmetic functions callable from GILDAS Variable sharing mechanism Call GILDAS from Python: pysic and py* modules >>> pysic.comm('command line') Specific functions (.exa(),...) Special attributes (.gdict) Documentation is available in GILDAS sources ( cookbooks/gildas/gildas-python.tex ) and on GILDAS web page ( > GILDAS > Doc > GILDAS-Python ) Ongoing work Test Windows port Support Python 3.0/3.1, adapt the internal binding 23/03/2010 GILDAS Python binding 10