ImageFileCollection

class ccdproc.ImageFileCollection(location=None, keywords=None, info_file=None)

Bases: object

Representation of a collection of image files.

The class offers a table summarizing values of keywords in the FITS headers of the files in the collection and offers convenient methods for iterating over the files in the collection. The generator methods use simple filtering syntax and can automate storage of any FITS files modified in the loop using the generator.

Parameters:

location : str, optional

path to directory containing FITS files

keywords : list of str or ‘*’, optional

Keywords that should be used as column headings in the summary table. If the value is or includes ‘*’ then all keywords that appear in any of the FITS headers of the files in the collection become table columns. Default value is ‘*’ unless info_file is specified.

info_file : str, optional

Path to file that contains a table of information about FITS files. In this case the keywords are set to the names of the columns of the info_file unless keywords is explicitly set to a different list.

Raises:

ValueError

Raised if keywords are set to a combination of ‘*’ and any other value.

Attributes Summary

files	list of str, Unfiltered list of FITS files in location.
keywords	list of str, Keywords currently in the summary table.
location	str, Path name to directory containing FITS files
summary
summary_info	Deprecated – use summary instead – astropy.table.Table of values of FITS keywords for files in the collection.

Methods Summary

data([do_not_scale_image_data])	Generator that yields each image in the collection.
files_filtered(**kwd)	Determine files whose keywords have listed values.
hdus([do_not_scale_image_data])	Generator that yields each HDU in the collection.
headers([do_not_scale_image_data])	Generator that yields each header in the collection.
refresh()	Refresh the collection by re-reading headers.
sort([keys])	Sort the list of files to determine the order of iteration.
values(keyword[, unique])	List of values for a keyword.

Attributes Documentation

files

list of str, Unfiltered list of FITS files in location.

keywords

list of str, Keywords currently in the summary table.

Setting the keywords causes the summary table to be regenerated unless the new keywords are a subset of the old.

location

str, Path name to directory containing FITS files

summary

summary_info

Deprecated – use summary instead – astropy.table.Table of values of FITS keywords for files in the collection.

Each keyword is a column heading. In addition, there is a column called ‘file’ that contains the name of the FITS file. The directory is not included as part of that name.

Methods Documentation

data(do_not_scale_image_data=False, **kwd)

Generator that yields each image in the collection.

If any of the parameters save_with_name, save_location or overwrite evaluates to True the generator will write a copy of each FITS file it is iterating over. In other words, if save_with_name and/or save_location is a string with non-zero length, and/or overwrite is True, a copy of each FITS file will be made.

Parameters:

save_with_name : str

string added to end of file name (before extension) if FITS file should be saved after iteration. Unless save_location is set, files will be saved to location of the source files self.location

save_location : str

Directory in which to save FITS files; implies that FITS files will be saved. Note this provides an easy way to copy a directory of files–loop over the image with save_location set.

overwrite : bool

If True, overwrite input FITS files.

do_not_scale_image_data : bool

If True, prevents fits from scaling images. Default is False.

return_fname : bool, default is False

If True, return the tuple (header, file_name) instead of just header. The file name returned is the name of the file only, not the full path to the file.

kwd : dict

Any additional keywords are used to filter the items returned; see Examples for details.

Returns:

numpy.ndarray

If return_fname is False, yield the next image in the collection

(numpy.ndarray, str)

If return_fname is True, yield a tuple of (image, file name) for the next item in the collection.

files_filtered(**kwd)

Determine files whose keywords have listed values.

**kwd is list of keywords and values the files must have.

If the keyword include_path=True is set, the returned list contains not just the filename, but the full path to each file.

The value ‘*’ represents any value.

A missing keyword is indicated by value ‘’

Example: >>> keys = [‘imagetyp’,’filter’] >>> collection = ImageFileCollection(‘test/data’, keywords=keys) >>> collection.files_filtered(imagetyp=’LIGHT’, filter=’R’) >>> collection.files_filtered(imagetyp=’*’, filter=’‘)

NOTE: Value comparison is case insensitive for strings.

hdus(do_not_scale_image_data=False, **kwd)

Generator that yields each HDU in the collection.

If any of the parameters save_with_name, save_location or overwrite evaluates to True the generator will write a copy of each FITS file it is iterating over. In other words, if save_with_name and/or save_location is a string with non-zero length, and/or overwrite is True, a copy of each FITS file will be made.

Parameters:

save_with_name : str

string added to end of file name (before extension) if FITS file should be saved after iteration. Unless save_location is set, files will be saved to location of the source files self.location

save_location : str

Directory in which to save FITS files; implies that FITS files will be saved. Note this provides an easy way to copy a directory of files–loop over the HDU with save_location set.

overwrite : bool

If True, overwrite input FITS files.

do_not_scale_image_data : bool

If True, prevents fits from scaling images. Default is False.

return_fname : bool, default is False

If True, return the tuple (header, file_name) instead of just header. The file name returned is the name of the file only, not the full path to the file.

kwd : dict

Any additional keywords are used to filter the items returned; see Examples for details.

Returns:

astropy.io.fits.HDU

If return_fname is False, yield the next HDU in the collection

(astropy.io.fits.HDU, str)

If return_fname is True, yield a tuple of (HDU, file name) for the next item in the collection.

headers(do_not_scale_image_data=True, **kwd)

Generator that yields each header in the collection.

If any of the parameters save_with_name, save_location or overwrite evaluates to True the generator will write a copy of each FITS file it is iterating over. In other words, if save_with_name and/or save_location is a string with non-zero length, and/or overwrite is True, a copy of each FITS file will be made.

Parameters:

save_with_name : str

string added to end of file name (before extension) if FITS file should be saved after iteration. Unless save_location is set, files will be saved to location of the source files self.location

save_location : str

Directory in which to save FITS files; implies that FITS files will be saved. Note this provides an easy way to copy a directory of files–loop over the header with save_location set.

overwrite : bool

If True, overwrite input FITS files.

do_not_scale_image_data : bool

If True, prevents fits from scaling images. Default is True.

return_fname : bool, default is False

If True, return the tuple (header, file_name) instead of just header. The file name returned is the name of the file only, not the full path to the file.

kwd : dict

Any additional keywords are used to filter the items returned; see Examples for details.

Returns:

astropy.io.fits.Header

If return_fname is False, yield the next header in the collection

(astropy.io.fits.Header, str)

If return_fname is True, yield a tuple of (header, file name) for the next item in the collection.

refresh()

Refresh the collection by re-reading headers.

sort(keys=None)

Sort the list of files to determine the order of iteration.

Sort the table of files according to one or more keys. This does not create a new object, instead is sorts in place.

Parameters:

keys : str or list of str

The key(s) to order the table by.

values(keyword, unique=False)

List of values for a keyword.

Parameters:

keyword : str

Keyword (i.e. table column) for which values are desired.

unique : bool, optional

If True, return only the unique values for the keyword.

Returns:

list

Values as a list.