pySLALIB v1.1.0 (Jan 2023)

pySLALIB provides interface for the Fortran version of P.T. Wallace's SLALIB positional astronomy library via f2py-generated (and hand-tweaked to eliminate unnecessary function/subroutine arguments) wrappers. SLALIB used to be hosted by the STARLINK site, although that service has been suspended. The version of SLALIB included here is 2.5-4 (with several additional tweaks) and is released under the GPL.

The python wrappers cover every function in SLALIB and a comprehensive set of unit tests are available in the test/ directory. The only external dependency is numpy (http://numpy.scipy.org). These wrappers are not related to the older (and apparently abandoned) pySLALIB that was once available on the Web (and which depended on Numeric as opposed to numpy).

Note: this version supports Windows (user must install mingw64-toolkit before building pySLALIB).

Build

Note: if not stated, commands are executed from repository directory.

• Windows

  Since version 1.1.0 building the pySLALIB is supported under Windows. This is available due to new build system meson-python via MinGW64 toolchain set of GCC compilers and libraries.

  Prerequisites

  • msys2 (https://www.msys2.org/)
  • mingw64-w64-toolchain (pacman -Syu mingw64-w64-toolchain from MSYS2 terminal)

  Steps

  1. Add E:\Programs\msys64\usr\bin (example path to /usr/bin directory in MSYS2 installation) to the PATH (powershell example):

     $Env:PATH="E:\Programs\msys64\usr\bin;" + $PATH
     

  2. Install python dependencies:

     pip install -r requirements.txt
     

  3. Run build:

     python -m build -w -n .
     

• Linux (Ubuntu 2x.04)

  pySLALIB natevily supports Linux.

  Prerequisites

  • python3-pip
  • build-essential
  • gfortran

  Steps

  1. Install system dependencies:

     sudo apt install build-essential python3-pip gfortran
     

  2. Install python dependencies:

     pip install -r requirements.txt
     

  3. Run build:

     python -m build -w -n .
     

All built wheels (.whl files) will be placed to the directory dist under current repository if parameter -o is not provided in #3 step. Note, tags are already passed all tests before uploading.

Installation

Most users will only need to do:

pip install <name-of-the-pyslalib-wheel>.whl

to generate the wrappers, build, and install the package. This method is preferrable since binary distributions are already uploaded for platforms Windows X86-64 and Linux X86-64. Otherwise one should build the packages before proceeding to the installation (see previous section).

Once pySLALIB is installed, you can run the unittests via:

  > python test/test_slalib.py

Example Usage (using IPython)

In [1]: import pyslalib as slalib

In [2]: slalib.sla_veri()
Out[2]: 2005004

In [3]: slalib.sla_caldj(1999, 12, 31)
Out[3]: (51543.0, 0)

In [4]: slalib.sla_etrms(1976.9)
Out[4]: array([ -1.62161710e-06,  -3.31007009e-07,  -1.43529663e-07])

In [5]: slalib.sla_fk45z(1.234, -0.123, 1984)
Out[5]: (1.2446165107316911, -0.12141858395865548)

In [6]: slalib.sla_dafin("-00 03 34.6", 1)
Out[6]: (12, -0.0010404101596610642, 0)

In [7]: slalib.sla_obs(0, "GBT")
Out[7]:
('GBT',
 'Green Bank Telescope                    ',
 1.3934679949996727,
 0.67078450520692623,
 880.0)

You can print the original Fortran doc strings using something like:

In [1]: from pyslalib import sla_caldj

In [2]: sla_caldj?
"""
*     - - - - - -
*      C A L D J
*     - - - - - -
*
*  Gregorian Calendar to Modified Julian Date
*
*  (Includes century default feature:  use sla_CLDJ for years
*   before 100AD.)
*
*  Given:
*     IY,IM,ID     int    year, month, day in Gregorian calendar
*
...

If you find any problems, please sent message to original developer Scott M. Ransom sransom@nrao.edu or this version contributor Nicolai S. Pankov nspankov@edu.hse.ru