HDU Lists

Inheritance diagram of HDUList

HDUList

class astropy.io.fits.HDUList(hdus=[], file=None)[source] [edit on github]

Bases: list, astropy.io.fits.verify._Verify

HDU list class. This is the top-level FITS object. When a FITS file is opened, a HDUList object is returned.

Construct a HDUList object.

Parameters:

hdus : sequence of HDU objects or single HDU, optional

The HDU object(s) to comprise the HDUList. Should be instances of HDU classes like ImageHDU or BinTableHDU.

file : file object, bytes, optional

The opened physical file associated with the HDUList or a bytes object containing the contents of the FITS file.

append(hdu)[source] [edit on github]

Append a new HDU to the HDUList.

Parameters:

hdu : HDU object

HDU to add to the HDUList.

close(output_verify=’exception’, verbose=False, closed=True)[source] [edit on github]

Close the associated FITS file and memmap object, if any.

Parameters:

output_verify : str

Output verification option. Must be one of "fix", "silentfix", "ignore", "warn", or "exception". May also be any combination of "fix" or "silentfix" with "+ignore", +warn, or +exception" (e.g. ``"fix+warn"). See Verification options for more info.

verbose : bool

When True, print out verbose messages.

closed : bool

When True, close the underlying file object.

fileinfo(index)[source] [edit on github]

Returns a dictionary detailing information about the locations of the indexed HDU within any associated file. The values are only valid after a read or write of the associated file with no intervening changes to the HDUList.

Parameters:

index : int

Index of HDU for which info is to be returned.

Returns:

fileinfo : dict or None

The dictionary details information about the locations of the indexed HDU within an associated file. Returns None when the HDU is not associated with a file.

Dictionary contents:

Key Value
file File object associated with the HDU
filename Name of associated file object
filemode Mode in which the file was opened (readonly, update, append, denywrite, ostream)
resized Flag that when True indicates that the data has been resized since the last read/write so the returned values may not be valid.
hdrLoc Starting byte location of header in file
datLoc Starting byte location of data block in file
datSpan Data size including padding
filename()[source] [edit on github]

Return the file name associated with the HDUList object if one exists. Otherwise returns None.

Returns:

filename : a string containing the file name associated with the

HDUList object if an association exists. Otherwise returns None.

flush(output_verify=’fix’, verbose=False)[source] [edit on github]

Force a write of the HDUList back to the file (for append and update modes only).

Parameters:

output_verify : str

Output verification option. Must be one of "fix", "silentfix", "ignore", "warn", or "exception". May also be any combination of "fix" or "silentfix" with "+ignore", +warn, or +exception" (e.g. ``"fix+warn"). See Verification options for more info.

verbose : bool

When True, print verbose messages

classmethod fromfile(fileobj, mode=None, memmap=None, save_backup=False, cache=True, lazy_load_hdus=True, **kwargs)[source] [edit on github]

Creates an HDUList instance from a file-like object.

The actual implementation of fitsopen(), and generally shouldn’t be used directly. Use open() instead (and see its documentation for details of the parameters accepted by this method).

classmethod fromstring(data, **kwargs)[source] [edit on github]

Creates an HDUList instance from a string or other in-memory data buffer containing an entire FITS file. Similar to HDUList.fromfile(), but does not accept the mode or memmap arguments, as they are only relevant to reading from a file on disk.

This is useful for interfacing with other libraries such as CFITSIO, and may also be useful for streaming applications.

Parameters:

data : str, buffer, memoryview, etc.

A string or other memory buffer containing an entire FITS file. It should be noted that if that memory is read-only (such as a Python string) the returned HDUList’s data portions will also be read-only.

kwargs : dict

Optional keyword arguments. See astropy.io.fits.open() for details.

Returns:

hdul : HDUList

An HDUList object representing the in-memory FITS file.

index_of(key)[source] [edit on github]

Get the index of an HDU from the HDUList.

Parameters:

key : int, str or tuple of (string, int)

The key identifying the HDU. If key is a tuple, it is of the form (key, ver) where ver is an EXTVER value that must match the HDU being searched for.

If the key is ambiguous (e.g. there are multiple ‘SCI’ extensions) the first match is returned. For a more precise match use the (name, ver) pair.

If even the (name, ver) pair is ambiguous (it shouldn’t be but it’s not impossible) the numeric index must be used to index the duplicate HDU.

Returns:

index : int

The index of the HDU in the HDUList.

info(output=None)[source] [edit on github]

Summarize the info of the HDUs in this HDUList.

Note that this function prints its results to the console—it does not return a value.

Parameters:

output : file, bool, optional

A file-like object to write the output to. If False, does not output to a file and instead returns a list of tuples representing the HDU info. Writes to sys.stdout by default.

insert(index, hdu)[source] [edit on github]

Insert an HDU into the HDUList at the given index.

Parameters:

index : int

Index before which to insert the new HDU.

hdu : HDU object

The HDU object to insert

readall()[source] [edit on github]

Read data of all HDUs into memory.

update_extend()[source] [edit on github]

Make sure that if the primary header needs the keyword EXTEND that it has it and it is correct.

writeto(fileobj, output_verify=’exception’, overwrite=False, checksum=False)[source] [edit on github]

Write the HDUList to a new file.

Parameters:

fileobj : file path, file object or file-like object

File to write to. If a file object, must be opened in a writeable mode.

output_verify : str

Output verification option. Must be one of "fix", "silentfix", "ignore", "warn", or "exception". May also be any combination of "fix" or "silentfix" with "+ignore", +warn, or +exception" (e.g. ``"fix+warn"). See Verification options for more info.

overwrite : bool, optional

If True, overwrite the output file if it exists. Raises an OSError (IOError for Python 2) if False and the output file exists. Default is False.

Changed in version 1.3: overwrite replaces the deprecated clobber argument.

checksum : bool

When True adds both DATASUM and CHECKSUM cards to the headers of all HDU’s written to the file.