Guide for Migrating to Astropy

Note

If you encounter any other issues not described here when migrating to Astropy, please let us know and we will update this guide accordingly.

Much of the functionality from ATpy has been incorporated into the Astropy as the astropy.table sub-package. The Astropy Table. class can be imported with:

>>> from astropy.table import Table

In the process of including the code in Astropy, the API has been changed in a backward-incompatible way, and the present document aims to describe the main changes.

Note that the Astropy Table class is more powerful than the ATpy equivalent in many respects, and we do not describe all the features here, only functionality of ATpy that has changed in Astropy. For a full overview of the Astropy Table class, see astropy.table.

Adding columns

In ATpy, columns are added with:

>>> from atpy import Table
>>> t = Table()
>>> t.add_column('a', [1, 2, 3])

In the Astropy 0.2.x Table class, the equivalent is:

>>> from astropy.table import Table, Column
>>> t = Table()
>>> t.add_column(Column(data=[1, 2, 3], name='a'))

This is a little more verbose, but from Astropy 0.3 onwards, this can be done more simply with:

>>> from astropy.table import Table, Column
>>> t = Table()
>>> t['a'] = [1, 2, 3]

This is already implemented in the latest developer version of Astropy, and will be the recommended way of adding columns.

Reading/writing

While it was possible to read a table directly into the Table class upon initialization in ATpy:

>>> from atpy import Table
>>> t = Table('test.fits')

Astropy now requires reading to be done by a class method:

>>> from astropy.table import Table
>>> t = Table.read('test.fits')

Writing should be similar between ATpy and Astropy:

>>> t.write('test.fits')

As of Astropy 0.2, Astropy can read/write the same ASCII formats as ATpy, as well as VO tables and HDF5. As of Astropy 0.3 (and in the current developer version of Astropy), FITS reading/writing is also implemented. This means that as of Astropy 0.3, the only features ATpy includes that are not supported by Astropy directly are the SQL input/output and the online (VO and IRSA) querying. However, the VO and IRSA querying will be possible with the new astroquery package which is currently under development.

Table Sets

Table sets are not implemented in Astropy at this time, but it is possible to simply loop over the tables in a file and construct a list or dictionary of them.