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This is the first "official" release. A patched version of cfitsio 3.28 is now
bundled. This will make it easier for folks to install, and provide a
consistent code base with which to develop. Thanks to Eli Rykoff for
suggesting a bundle. Thanks to Eli and Martin White for helping extensively
with testing.
On OS X, we now link properly with universal binaries on intel. Thanks to Eli
Rykoff for help with OS X testing and bug fixes.
New features
- Write and read variable length columns. When writing a table, any fields
declared "object" ("O" type char) in the input array will be written to a
variable length column. For numbers, this means vectors of varying
length. For strings, it means varying length strings.
When reading, there are two options. 1) By default the data are read
into fixed length fields with padding to the maximum size in the table
column. This is a "least surprise" approach, since fancy indexing and
other array ops will work as expectd. 2) To save memory, construct the
FITS object with vstorage='object' to store the data as objects. This
storage can also be written back out to a new FITS file with variable
length columns. You can also over-ride the default vstorage when calling
read functions.
- Write and read ascii tables. cfitsio supports writing scalar 2- and
4-byte integers, floats and doubles. But for reading only 4-byte integers
and doubles are supported, presumably because of the ambiguity in the
tform fields. Scalar strings are fully supported in both reading and
writing. No array fields are supported for ascii.
- Append rows to an existing table using the append method.
>>> fits.write_table(data1)
>>> fits[-1].append(data2)
- Using the new "where" method, you can select rows in a table where an
input expression evaluates to true. The table is scanned row by row
without a large read. This is surprisingly fast, and useful for figuring
out what sections of a large file you want to extract. only requires
enough memory to hold the row indices.
>>> w=fits[ext].where('x > 3 && y < 25')
>>> data=fits[ext].read(rows=w)
>>> data=fits[ext][w]
- You can now read rows and columns from a table HDU using slice notation. e.g.
to read row subsets from extension 1
>>> fits=fitsio.FITS(filename)
>>> data=fits[1][:]
>>> data=fits[1][10:30]
>>> data=fits[1][10:30:2]
You can also specify a list of rows
>>> rows=[3,8,25]
>>> data=fits[1][rows]
This is equivalent to
>>> data=fits[1].read(rows=rows)
To get columns subsets, the notation is similar. The data are read
when the rows are specified. If a sequence of columns is entered,
a recarray is returned, otherwise a simple array.
>>> data=fits[1]['x'][:]
>>> data=fits[1]['x','y'][3:20]
>>> data=fits[1][column_list][row_list]
- Added support for EXTVER header keywords. When choosing an HDU by name,
this allows one to select among HDUs that have the same name. Thanks to
Eli Rykoff for suggesting this feature and helping with testing.
- Name matching for table columns and extension names is not
case-insensitive by default. You can turn on case sensitivity by
constructing the FITS object with case_sensitive=True, or sending
that keyword to the convenience functions read and read_header.
- Added write_checksum method to the FITSHDU class, which computes the
checksum for the HDU, both the data portion alone (DATASUM keyword)
and the checksum complement for the entire HDU (CHECKSUM).
- Added an extensive test suite. Use this to run the tests
fitsio.test.test()
- Added fitsio.cfitsio_version() function, returns the cfitsio
version as a string.
- added read_slice method, which is used to implement the slice
notation introduced above.
significant code changes
- Now using fits_read_tblbytes when reading all rows and columns. This
is just as fast but does not bypass, and thus confuse, the read buffers.
- Removed many direct uses of the internal cfitsio struct objects,
preferring to use provided access functions. This allowed compilation
on older cfitsio that had different struct representations.
bug fixes
- too many to list in this early release.