Miscellaneous Features¶
In this chapter, we’ll describe some of the miscellaneous features of PyFITS.
Warning Messages¶
PyFITS uses the Python warnings module to issue warning messages. The user can
suppress the warnings using the python command line argument -W"ignore"
when starting an interactive python session. For example:
python -W"ignore"
The user may also use the command line argument when running a python script as follows:
python -W"ignore" myscript.py
It is also possible to suppress warnings from within a python script. For instance, the warnings issued from a single call to the writeto convenience function may be suppressed from within a python script as follows:
import warnings
import pyfits
# ...
warnings.resetwarnings()
warnings.filterwarnings('ignore', category=UserWarning, append=True)
pyfits.writeto(file, im, clobber=True)
warnings.resetwarnings()
warnings.filterwarnings('always', category=UserWarning, append=True)
# ...
PyFITS also issues warnings when deprecated API features are used. In Python
2.7 and up deprecation warnings are ignored by default. To run Python with
deprecation warnings enabled, either start Python with the -Wall
argument,
or you can enable deprecation warnings specifically with -Wd
.
In Python versions below 2.7, if you wish to squelch deprecation warnings,
you can start Python with -Wi::Deprecation
. This sets all deprecation
warnings to ignored. See
http://docs.python.org/using/cmdline.html#cmdoption-unittest-discover-W
for more information on the -W argument.
Differs¶
The pyfits.diff
module contains several facilities for generating and
reporting the differences between two FITS files, or two components of a FITS
file.
The FITSDiff
class can be used to generate and represent the
differences between either two FITS files on disk, or two existing
HDUList
objects (or some combination thereof).
Likewise, the HeaderDiff
class can be used to find the differences
just between two Header
objects. Other available differs include
HDUDiff
, ImageDataDiff
, TableDataDiff
, and
RawDataDiff
.
Each of these classes are instantiated with two instances of the objects that
they diff. The returned diff instance has a number of attributes starting with
.diff_
that describe differences between the two objects. See the API
documentation for details on the different differ classes.