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FITS (Flexible Image Transport System) is a data format most used in astronomy. PyFITS is a Python module for reading, writing, and manipulating FITS files. The module uses Python's object-oriented features to provide quick, easy, and efficient access to FITS files. The use of Python's array syntax enables immediate access to any FITS extension, header cards, or data items. Changes to 2.4.0 (in py-pyfits): Changelog =========== 3.2 (2013-11-26) ---------------- Highlights ^^^^^^^^^^ - Rewrote CFITSIO-based backend for handling tile compression of FITS files. It now uses a standard CFITSIO instead of heavily modified pieces of CFITSIO as before. PyFITS ships with its own copy of CFITSIO v3.35 which supports the latest version of the Tiled Image Convention (v2.3), but system packagers may choose instead to strip this out in favor of a system-installed version of CFITSIO. Earlier versions may work, but nothing earlier than 3.28 has been tested yet. (#169) - Added support for reading and writing tables using the Q format for columns. The Q format is identical to the P format (variable-length arrays) except that it uses 64-bit integers for the data descriptors, allowing more than 4 GB of variable-length array data in a single table. (#160) - Added initial support for table columns containing pseudo-unsigned integers. This is currently enabled by using the ``uint=True`` option when opening files; any table columns with the correct BZERO value will be interpreted and returned as arrays of unsigned integers. - Some refactoring of the table and ``FITS_rec`` modules in order to better separate the details of the FITS binary and ASCII table data structures from the HDU data structures that encapsulate them. Most of these changes should not be apparent to users (but see API Changes below). API Changes ^^^^^^^^^^^ - Assigning to values in ``ColDefs.names``, ``ColDefs.formats``, ``ColDefs.nulls`` and other attributes of ``ColDefs`` instances that return lists of column properties is no longer supported. Assigning to those lists will no longer update the corresponding columns. Instead, please just modify the ``Column`` instances directly (``Column.name``, ``Column.null``, etc.) - The ``pyfits.new_table`` function is marked "pending deprecation". This does not mean it will be removed outright or that its functionality has changed. It will likely be replaced in the future for a function with similar, if not subtly different functionality. A better, if not slightly more verbose approach is to use ``pyfits.FITS_rec.from_columns`` to create a new ``FITS_rec`` table--this has the same interface as ``pyfits.new_table``. The difference is that it returns a plan ``FITS_rec`` array, and not an HDU instance. This ``FITS_rec`` object can then be used as the data argument in the constructors for ``BinTableHDU`` (for binary tables) or ``TableHDU`` (for ASCII tables). This is analogous to creating an ``ImageHDU`` by passing in an image array. ``pyfits.FITS_rec.from_columns`` is just a simpler way of creating a FITS-compatible recarray from a FITS column specification. - The ``updateHeader``, ``updateHeaderData``, and ``updateCompressedData`` methods of the ``CompDataHDU`` class are pending deprecation and moved to internal methods. The operation of these methods depended too much on internal state to be used safely by users; instead they are invoked automatically in the appropriate places when reading/writing compressed image HDUs. - The ``CompDataHDU.compData`` attribute is pending deprecation in favor of the clearer and more PEP-8 compatible ``CompDataHDU.compressed_data``. - The constructor for ``CompDataHDU`` has been changed to accept new keyword arguments. The new keyword arguments are essentially the same, but are in underscore_separated format rather than camelCase format. The old arguments are still pending deprecation. - The internal attributes of HDU classes ``_hdrLoc``, ``_datLoc``, and ``_datSpan`` have been replaced with ``_header_offset``, ``_data_offset``, and ``_data_size`` respectively. The old attribute names are still pending deprecation. This should only be of interest to advanced users who have created their own HDU subclasses. - The following previously deprecated functions and methods have been removed entirely: ``createCard``, ``createCardFromString``, ``upperKey``, ``ColDefs.data``, ``setExtensionNameCaseSensitive``, ``_File.getfile``, ``_TableBaseHDU.get_coldefs``, ``Header.has_key``, ``Header.ascardlist``. If you run your code with a previous version of PyFITS (>= 3.0, < 3.2) with the ``python -Wd`` argument, warnings for all deprecated interfaces still in use will be displayed. - Interfaces that were pending deprecation are now fully deprecated. These include: ``create_card``, ``create_card_from_string``, ``upper_key``, ``Header.get_history``, and ``Header.get_comment``. - The ``.name`` attribute on HDUs is now directly tied to the HDU's header, so that if ``.header['EXTNAME']`` changes so does ``.name`` and vice-versa. - The ``pyfits.file.PYTHON_MODES`` constant dict was renamed to ``pyfits.file.PYFITS_MODES`` which better reflects its purpose. This is rarely used by client code, however. Support for the old name will be removed by PyFITS 3.4. Other Changes and Additions ^^^^^^^^^^^^^^^^^^^^^^^^^^^ - The new compression code also adds support for the ZQUANTIZ and ZDITHER0 keywords added in more recent versions of this FITS Tile Compression spec. This includes support for lossless compression with GZIP. (#198) By default no dithering is used, but the ``SUBTRACTIVE_DITHER_1`` and ``SUBTRACTIVE_DITHER_2`` methods can be enabled by passing the correct constants to the ``quantize_method`` argument to the ``CompImageHDU`` constuctor. A seed can be manually specified, or automatically generated using either the system clock or checksum-based methods via the ``dither_seed`` argument. See the documentation for ``CompImageHDU`` for more details. (#198) (spacetelescope/PYFITS#32) - Images compressed with the Tile Compression standard can now be larger than 4 GB through support of the Q format. (#159) - All HDUs now have a ``.ver`` ``.level`` attribute that returns the value of the EXTVAL and EXTLEVEL keywords from that HDU's header, if the exist. This was added for consistency with the ``.name`` attribute which returns the EXTNAME value from the header. - Then ``Column`` and ``ColDefs`` classes have new ``.dtype`` attributes which give the Numpy dtype for the column data in the first case, and the full Numpy compound dtype for each table row in the latter case. - There was an issue where new tables created defaulted the values in all string columns to '0.0'. Now string columns are filled with empty strings by default--this seems a less surprising default, but it may cause differences with tables created with older versions of PyFITS. - Improved round-tripping and preservation of manually assigned column attributes (``TNULLn``, ``TSCALn``, etc.) in table HDU headers. (astropy/astropy#996) Bug Fixes ^^^^^^^^^ - Binary tables containing compressed images may, optionally, contain other columns unrelated to the tile compression convention. Although this is an uncommon use case, it is permitted by the standard. (#159) - Reworked some of the file I/O routines to allow simpler, more consistent mapping between OS-level file modes ('rb', 'wb', 'ab', etc.) and the more "PyFITS-specific" modes used by PyFITS like "readonly" and "update". That is, if reading a FITS file from an open file object, it doesn't matter as much what "mode" it was opened in so long as it has the right capabilities (read/write/etc.) Also works around bugs in the Python io module in 2.6+ with regard to file modes. (spacetelescope/PyFITS#33) - Fixed an obscure issue that can occur on systems that don't have flush to memory-mapped files implemented (namely GNU Hurd). (astropy/astropy#968) 3.1.3 (2013-11-26) ------------------ - Disallowed assigning NaN and Inf floating point values as header values, since the FITS standard does not define a way to represent them in. Because this is undefined, the previous behavior did not make sense and produced invalid FITS files. (spacetelescope/PyFITS#11) - Added a workaround for a bug in 64-bit OSX that could cause truncation when writing files greater than 2^32 bytes in size. (spacetelescope/PyFITS#28) - Fixed a long-standing issue where writing binary tables did not correctly write the TFORMn keywords for variable-length array columns (they ommitted the max array length parameter of the format). This was thought fixed in v3.1.2, but it was only fixed there for compressed image HDUs and not for binary tables in general. - Fixed an obscure issue that can occur on systems that don't have flush to memory-mapped files implemented (namely GNU Hurd). (Backported from 3.2) 3.0.12 (2013-11-26) ------------------- - Disallowed assigning NaN and Inf floating point values as header values, since the FITS standard does not define a way to represent them in. Because this is undefined, the previous behavior did not make sense and produced invalid FITS files. (Backported from 3.1.3) - Added a workaround for a bug in 64-bit OSX that could cause truncation when writing files greater than 2^32 bytes in size. (Backported from 3.1.3) - Fixed a long-standing issue where writing binary tables did not correctly write the TFORMn keywords for variable-length array columns (they ommitted the max array length parameter of the format). This was thought fixed in v3.1.2, but it was only fixed there for compressed image HDUs and not for binary tables in general. (Backported from 3.1.3) - Fixed an obscure issue that can occur on systems that don't have flush to memory-mapped files implemented (namely GNU Hurd). (Backported from 3.2) 3.1.2 (2013-04-22) ------------------ - When an error occurs opening a file in fitsdiff the exception message will now at least mention which file had the error. (#168) - Fixed support for opening gzipped FITS files by filename in a writeable mode (PyFITS has supported writing to gzip files for some time now, but only enabled it when GzipFile objects were passed to ``pyfits.open()`` due to some legacy code preventing full gzip support. (#195) - Added a more helpful error message in the case of malformatted FITS files that contain non-float NULL values in an ASCII table but are missing the required TNULLn keywords in the header. (#197) - Fixed an (apparently long-standing) issue where writing compressed images did not correctly write the TFORMn keywords for variable-length array columns (they ommitted the max array length parameter of the format). (#199) - Slightly refactored how tables containing variable-length array columns are handled to add two improvements: Fixes an issue where accessing the data after a call to the `pyfits.getdata` convenience function caused an exception, and allows the VLA data to be read from an existing mmap of the FITS file. (#200) - Fixed a bug that could occur when opening a table containing multi-dimensional columns (i.e. via the TDIMn keyword) and then writing it out to a new file. (#201) - Added use of the console_scripts entry point to install the fitsdiff and fitscheck scripts, which if nothing else provides better Windows support. The generated scripts now override the ones explicitly defined in the scripts/ directory (which were just trivial stubs to begin with). (#202) - Fixed a bug on Python 3 where attempting to open a non-existent file on Python 3 caused a seemingly unrelated traceback. (#203) - Fixed a bug in fitsdiff that reported two header keywords containing NaN as value as different. (#204) - Fixed an issue in the tests that caused some tests to fail if pyfits is installed with read-only permissions. (#208) - Fixed a bug where instantiating a ``BinTableHDU`` from a numpy array containing boolean fields converted all the values to ``False``. (#215) - Fixed an issue where passing an array of integers into the constructor of ``Column()`` when the column type is floats of the same byte width caused the column array to become garbled. (#218) - Fixed inconsistent behavior in creating CONTINUE cards from byte strings versus unicode strings in Python 2--CONTINUE cards can now be created properly from unicode strings (so long as they are convertable to ASCII). (spacetelescope/PyFITS#1) - Fixed a couple cases where creating a new table using TDIMn in some of the columns could caused a crash. (spacetelescope/PyFITS#3) - Fixed a bug in parsing HIERARCH keywords that do not have a space after the first equals sign (before the value). (spacetelescope/PyFITS#5) - Prevented extra leading whitespace on HIERARCH keywords from being treated as part of the keyword. (spacetelescope/PyFITS#6) - Fixed a bug where HIERARCH keywords containing lower-case letters was mistakenly marked as invalid during header validation. (spacetelescope/PyFITS#7) - Fixed an issue that was ancillary to (spacetelescope/PyFITS#7) where the ``Header.index()`` method did not work correctly with HIERARCH keywords containing lower-case letters. 3.0.11 (2013-04-17) ------------------- - Fixed support for opening gzipped FITS files by filename in a writeable mode (PyFITS has supported writing to gzip files for some time now, but only enabled it when GzipFile objects were passed to ``pyfits.open()`` due to some legacy code preventing full gzip support. Backported from 3.1.2. (#195) - Added a more helpful error message in the case of malformatted FITS files that contain non-float NULL values in an ASCII table but are missing the required TNULLn keywords in the header. Backported from 3.1.2. (#197) - Fixed an (apparently long-standing) issue where writing compressed images did not correctly write the TFORMn keywords for variable-length array columns (they ommitted the max array length parameter of the format). Backported from 3.1.2. (#199) - Slightly refactored how tables containing variable-length array columns are handled to add two improvements: Fixes an issue where accessing the data after a call to the `pyfits.getdata` convenience function caused an exception, and allows the VLA data to be read from an existing mmap of the FITS file. Backported from 3.1.2. (#200) - Fixed a bug that could occur when opening a table containing multi-dimensional columns (i.e. via the TDIMn keyword) and then writing it out to a new file. Backported from 3.1.2. (#201) - Fixed a bug on Python 3 where attempting to open a non-existent file on Python 3 caused a seemingly unrelated traceback. Backported from 3.1.2. (#203) - Fixed a bug in fitsdiff that reported two header keywords containing NaN as value as different. Backported from 3.1.2. (#204) - Fixed an issue in the tests that caused some tests to fail if pyfits is installed with read-only permissions. Backported from 3.1.2. (#208) - Fixed a bug where instantiating a ``BinTableHDU`` from a numpy array containing boolean fields converted all the values to ``False``. Backported from 3.1.2. (#215) - Fixed an issue where passing an array of integers into the constructor of ``Column()`` when the column type is floats of the same byte width caused the column array to become garbled. Backported from 3.1.2. (#218) - Fixed a couple cases where creating a new table using TDIMn in some of the columns could caused a crash. Backported from 3.1.2. (spacetelescope/PyFITS#3) 3.1.1 (2013-01-02) ------------------ This is a bug fix release for the 3.1.x series. Bug Fixes ^^^^^^^^^ - Improved handling of scaled images and pseudo-unsigned integer images in compressed image HDUs. They now work more transparently like normal image HDUs with support for the ``do_not_scale_image_data`` and ``uint`` options, as well as ``scale_back`` and ``save_backup``. The ``.scale()`` method works better too. (#88) - Permits non-string values for the EXTNAME keyword when reading in a file, rather than throwing an exception due to the malformatting. Added verification for the format of the EXTNAME keyword when writing. (#96) - Added support for EXTNAME and EXTVER in PRIMARY HDUs. That is, if EXTNAME is specified in the header, it will also be reflected in the ``.name`` attribute and in ``pyfits.info()``. These keywords used to be verboten in PRIMARY HDUs, but the latest version of the FITS standard allows them. (#151) - HCOMPRESS can again be used to compress data cubes (and higher-dimensional arrays) so long as the tile size is effectively 2-dimensional. In fact, PyFITS will automatically use compatible tile sizes even if they're not explicitly specified. (#171) - Added support for the optional ``endcard`` parameter in the ``Header.fromtextfile()`` and ``Header.totextfile()`` methods. Although ``endcard=False`` was a reasonable default assumption, there are still text dumps of FITS headers that include the END card, so this should have been more flexible. (#176) - Fixed a crash when running fitsdiff on two empty (that is, zero row) tables. (#178) - Fixed an issue where opening files containing random groups HDUs in update mode could cause an unnecessary rewrite of the file even if none of the data is modified. (#179) - Fixed a bug that could caused a deadlock in the filesystem on OSX if PyFITS is used with Numpy 1.7 in some cases. (#180) - Fixed a crash when generating diff reports from diffs using the ``ignore_comments`` options. (#181) - Fixed some bugs with WCS Paper IV record-valued keyword cards: - Cards that looked kind of like RVKCs but were not intended to be were over-permissively treated as such--commentary keywords like COMMENT and HISTORY were particularly affected. (#183) - Looking up a card in a header by its standard FITS keyword only should always return the raw value of that card. That way cards containing values that happen to valid RVKCs but were not intended to be will still be treated like normal cards. (#184) - Looking up a RVKC in a header with only part of the field-specifier (for example "DP1.AXIS" instead of "DP1.AXIS.1") was implicitly treated as a wildcard lookup. (#184) - Fixed a crash when diffing two FITS files where at least one contains a compressed image HDU which was not recognized as an image instead of a table. (#187) - Fixed bugs in the backwards compatibility layer for the ``CardList.index`` and ``CardList.count`` methods. (#190) - Improved ``__repr__`` and text file representation of cards with long values that are split into CONTINUE cards. (#193) - Fixed a crash when trying to assign a long (> 72 character) value to blank ('') keywords. This also changed how blank keywords are represented--there are still exactly 8 spaces before any commentary content can begin; this *may* affect the exact display of header cards that assumed there could be fewer spaces in a blank keyword card before the content begins. However, the current approach is more in line with the requirements of the FITS standard. (#194) 3.0.10 (2013-01-02) ------------------- - Improved handling of scaled images and pseudo-unsigned integer images in compressed image HDUs. They now work more transparently like normal image HDUs with support for the ``do_not_scale_image_data`` and ``uint`` options, as well as ``scale_back`` and ``save_backup``. The ``.scale()`` method works better too. Backported from 3.1.1. (#88) - Permits non-string values for the EXTNAME keyword when reading in a file, rather than throwing an exception due to the malformatting. Added verification for the format of the EXTNAME keyword when writing. Backported from 3.1.1. (#96) - Added support for EXTNAME and EXTVER in PRIMARY HDUs. That is, if EXTNAME is specified in the header, it will also be reflected in the ``.name`` attribute and in ``pyfits.info()``. These keywords used to be verbotten in PRIMARY HDUs, but the latest version of the FITS standard allows them. Backported from 3.1.1. (#151) - HCOMPRESS can again be used to compress data cubes (and higher-dimensional arrays) so long as the tile size is effectively 2-dimensional. In fact, PyFITS will not automatically use compatible tile sizes even if they're not explicitly specified. Backported from 3.1.1. (#171) - Fixed a bug when writing out files containing zero-width table columns, where the TFIELDS keyword would be updated incorrectly, leaving the table largely unreadable. Backported from 3.1.0. (#174) - Fixed an issue where opening files containing random groups HDUs in update mode could cause an unnecessary rewrite of the file even if none of the data is modified. Backported from 3.1.1. (#179) - Fixed a bug that could caused a deadlock in the filesystem on OSX if PyFITS is used with Numpy 1.7 in some cases. Backported from 3.1.1. (#180) 3.1 (2012-08-08) ---------------- Highlights ^^^^^^^^^^ - The ``Header`` object has been significantly reworked, and ``CardList`` objects are now deprecated (their functionality folded into the ``Header`` class). See API Changes below for more details. - Memory maps are now used by default to access HDU data. See API Changes below for more details. - Now includes a new version of the ``fitsdiff`` program for comparing two FITS files, and a new FITS comparison API used by ``fitsdiff``. See New Features below. API Changes ^^^^^^^^^^^ - The ``Header`` class has been rewritten, and the ``CardList`` class is deprecated. Most of the basic details of working with FITS headers are unchanged, and will not be noticed by most users. But there are differences in some areas that will be of interest to advanced users, and to application developers. For full details of the changes, see the "Header Interface Transition Guide" section in the PyFITS documentation. See ticket #64 on the PyFITS Trac for futher details and background. Some highlights are listed below: * The Header class now fully implements the Python dict interface, and can be used interchangably with a dict, where the keys are header keywords. * New keywords can be added to the header using normal keyword assignment (previously it was necessary to use ``Header.update`` to add new keywords). For example:: >>> header['NAXIS'] = 2 will update the existing 'FOO' keyword if it already exists, or add a new one if it doesn't exist, just like a dict. * It is possible to assign both a value and a comment at the same time using a tuple:: >>> header['NAXIS'] = (2, 'Number of axes') * To add/update a new card and ensure it's added in a specific location, use ``Header.set()``:: >>> header.set('NAXIS', 2, 'Number of axes', after='BITPIX') This works the same as the old ``Header.update()``. ``Header.update()`` still works in the old way too, but is deprecated. * Although ``Card`` objects still exist, it generally is not necessary to work with them directly. ``Header.ascardlist()``/``Header.ascard`` are deprecated and should not be used. To directly access the ``Card`` objects in a header, use ``Header.cards``. * To access card comments, it is still possible to either go through the card itself, or through ``Header.comments``. For example:: >>> header.cards['NAXIS'].comment Number of axes >>> header.comments['NAXIS'] Number of axes * ``Card`` objects can now be used interchangeably with ``(keyword, value, comment)`` 3-tuples. They still have ``.value`` and ``.comment`` attributes as well. The ``.key`` attribute has been renamed to ``.keyword`` for consistency, though ``.key`` is still supported (but deprecated). - Memory mapping is now used by default to access HDU data. That is, ``pyfits.open()`` uses ``memmap=True`` as the default. This provides better performance in the majority of use cases--there are only some I/O intensive applications where it might not be desirable. Enabling mmap by default also enabled finding and fixing a large number of bugs in PyFITS' handling of memory-mapped data (most of these bug fixes were backported to PyFITS 3.0.5). (#85) * A new ``pyfits.USE_MEMMAP`` global variable was added. Set ``pyfits.USE_MEMMAP = False`` to change the default memmap setting for opening files. This is especially useful for controlling the behavior in applications where pyfits is deeply embedded. * Likewise, a new ``PYFITS_USE_MEMMAP`` environment variable is supported. Set ``PYFITS_USE_MEMMAP = 0`` in your environment to change the default behavior. - The ``size()`` method on HDU objects is now a ``.size`` property--this returns the size in bytes of the data portion of the HDU, and in most cases is equivalent to ``hdu.data.nbytes`` (#83) - ``BinTableHDU.tdump`` and ``BinTableHDU.tcreate`` are deprecated--use ``BinTableHDU.dump`` and ``BinTableHDU.load`` instead. The new methods output the table data in a slightly different format from previous versions, which places quotes around each value. This format is compatible with data dumps from previous versions of PyFITS, but not vice-versa due to a parsing bug in older versions. - Likewise the ``pyfits.tdump`` and ``pyfits.tcreate`` convenience function versions of these methods have been renamed ``pyfits.tabledump`` and ``pyfits.tableload``. The old deprecated, but currently retained for backwards compatibility. (r1125) - A new global variable ``pyfits.EXTENSION_NAME_CASE_SENSITIVE`` was added. This serves as a replacement for ``pyfits.setExtensionNameCaseSensitive`` which is not deprecated and may be removed in a future version. To enable case-sensitivity of extension names (i.e. treat 'sci' as distict from 'SCI') set ``pyfits.EXTENSION_NAME_CASE_SENSITIVE = True``. The default is ``False``. (r1139) - A new global configuration variable ``pyfits.STRIP_HEADER_WHITESPACE`` was added. By default, if a string value in a header contains trailing whitespace, that whitespace is automatically removed when the value is read. Now if you set ``pyfits.STRIP_HEADER_WHITESPACE = False`` all whitespace is preserved. (#146) - The old ``classExtensions`` extension mechanism (which was deprecated in PyFITS 3.0) is removed outright. To our knowledge it was no longer used anywhere. (r1309) - Warning messages from PyFITS issued through the Python warnings API are now output to stderr instead of stdout, as is the default. PyFITS no longer modifies the default behavior of the warnings module with respect to which stream it outputs to. (r1319) - The ``checksum`` argument to ``pyfits.open()`` now accepts a value of 'remove', which causes any existing CHECKSUM/DATASUM keywords to be ignored, and removed when the file is saved. New Features ^^^^^^^^^^^^ - Added support for the proposed "FITS" extension HDU type. See http://listmgr.cv.nrao.edu/pipermail/fitsbits/2002-April/001094.html. FITS HDUs contain an entire FITS file embedded in their data section. `FitsHDU` objects work like other HDU types in PyFITS. Their ``.data`` attribute returns the raw data array. However, they have a special ``.hdulist`` attribute which processes the data as a FITS file and returns it as an in-memory HDUList object. FitsHDU objects also support a ``FitsHDU.fromhdulist()`` classmethod which returns a new `FitsHDU` object that embeds the supplied HDUList. (#80) - Added a new ``.is_image`` attribute on HDU objects, which is True if the HDU data is an 'image' as opposed to a table or something else. Here the meaning of 'image' is fairly loose, and mostly just means a Primary or Image extension HDU, or possibly a compressed image HDU (#71) - Added an ``HDUList.fromstring`` classmethod which can parse a FITS file already in memory and instantiate and ``HDUList`` object from it. This could be useful for integrating PyFITS with other libraries that work on FITS file, such as CFITSIO. It may also be useful in streaming applications. The name is a slight misnomer, in that it actually accepts any Python object that implements the buffer interface, which includes ``bytes``, ``bytearray``, ``memoryview``, ``numpy.ndarray``, etc. (#90) - Added a new ``pyfits.diff`` module which contains facilities for comparing FITS files. One can use the ``pyfits.diff.FITSDiff`` class to compare two FITS files in their entirety. There is also a ``pyfits.diff.HeaderDiff`` class for just comparing two FITS headers, and other similar interfaces. See the PyFITS Documentation for more details on this interface. The ``pyfits.diff`` module powers the new ``fitsdiff`` program installed with PyFITS. After installing PyFITS, run ``fitsdiff --help`` for usage details. - ``pyfits.open()`` now accepts a ``scale_back`` argument. If set to ``True``, this automatically scales the data using the original BZERO and BSCALE parameters the file had when it was first opened, if any, as well as the original BITPIX. For example, if the original BITPIX were 16, this would be equivalent to calling ``hdu.scale('int16', 'old')`` just before calling ``flush()`` or ``close()`` on the file. This option applies to all HDUs in the file. (#120) - ``pyfits.open()`` now accepts a ``save_backup`` argument. If set to ``True``, this automatically saves a backup of the original file before flushing any changes to it (this of course only applies to update and append mode). This may be especially useful when working with scaled image data. (#121) Changes in Behavior ^^^^^^^^^^^^^^^^^^^ - Warnings from PyFITS are not output to stderr by default, instead of stdout as it has been for some time. This is contrary to most users' expectations and makes it more difficult for them to separate output from PyFITS from the desired output for their scripts. (r1319) Bug Fixes ^^^^^^^^^ - Fixed ``pyfits.tcreate()`` (now ``pyfits.tableload()``) to be more robust when encountering blank lines in a column definition file (#14) - Fixed a fairly rare crash that could occur in the handling of CONTINUE cards when using Numpy 1.4 or lower (though 1.4 is the oldest version supported by PyFITS). (r1330) - Fixed ``_BaseHDU.fromstring`` to actually correctly instantiate an HDU object from a string/buffer containing the header and data of that HDU. This allowed for the implementation of ``HDUList.fromstring`` described above. (#90) - Fixed a rare corner case where, in some use cases, (mildly, recoverably) malformatted float values in headers were not properly returned as floats. (#137) - Fixed a corollary to the previous bug where float values with a leading zero before the decimal point had the leading zero unnecessarily removed when saving changes to the file (eg. "0.001" would be written back as ".001" even if no changes were otherwise made to the file). (#137) - When opening a file containing CHECKSUM and/or DATASUM keywords in update mode, the CHECKSUM/DATASUM are updated and preserved even if the file was opened with checksum=False. This change in behavior prevents checksums from being unintentionally removed. (#148) - Fixed a bug where ``ImageHDU.scale(option='old')`` wasn't working at all--it was not restoring the image to its original BSCALE and BZERO values. (#162) - Fixed a bug when writing out files containing zero-width table columns, where the TFIELDS keyword would be updated incorrectly, leaving the table largely unreadable. This fix will be backported to the 3.0.x series in version 3.0.10. (#174) 3.0.9 (2012-08-06) ------------------ This is a bug fix release for the 3.0.x series. Bug Fixes ^^^^^^^^^ - Fixed ``Header.values()``/``Header.itervalues()`` and ``Header.items()``/ ``Header.iteritems()`` to correctly return the different values for duplicate keywords (particularly commentary keywords like HISTORY and COMMENT). This makes the old Header implementation slightly more compatible with the new implementation in PyFITS 3.1. (#127) .. note:: This fix did not change the existing behavior from earlier PyFITS versions where ``Header.keys()`` returns all keywords in the header with duplicates removed. PyFITS 3.1 changes that behavior, so that ``Header.keys()`` includes duplicates. - Fixed a bug where ``ImageHDU.scale(option='old')`` wasn't working at all--it was not restoring the image to its original BSCALE and BZERO values. (#162) - Fixed a bug where opening a file containing compressed image HDUs in 'update' mode and then immediately closing it without making any changes caused the file to be rewritten unncessarily. (#167) - Fixed two memory leaks that could occur when writing compressed image data, or in some cases when opening files containing compressed image HDUs in 'update' mode. (#168) 3.0.8 (2012-06-04) ------------------ Changes in Behavior ^^^^^^^^^^^^^^^^^^^ - Prior to this release, image data sections did not work with scaled data--that is, images with non-trivial BSCALE and/or BZERO values. Previously, in order to read such images in sections, it was necessary to manually apply the BSCALE+BZERO to each section. It's worth noting that sections *did* support pseudo-unsigned ints (flakily). This change just extends that support for general BSCALE+BZERO values. Bug Fixes ^^^^^^^^^ - Fixed a bug that prevented updates to values in boolean table columns from being saved. This turned out to be a symptom of a deeper problem that could prevent other table updates from being saved as well. (#139) - Fixed a corner case in which a keyword comment ending with the string "END" could, in some circumstances, cause headers (and the rest of the file after that point) to be misread. (#142) - Fixed support for scaled image data and psuedo-unsigned ints in image data sections (``hdu.section``). Previously this was not supported at all. At some point support was supposedly added, but it was buggy and incomplete. Now the feature seems to work much better. (#143) - Fixed the documentation to point out that image data sections *do* support non-contiguous slices (and have for a long time). The documentation was never updated to reflect this, and misinformed users that only contiguous slices were supported, leading to some confusion. (#144) - Fixed a bug where creating an ``HDUList`` object containing multiple PRIMARY HDUs caused an infinite recursion when validating the object prior to writing to a file. (#145) - Fixed a rare but serious case where saving an update to a file that previously had a CHECKSUM and/or DATASUM keyword, but removed the checksum in saving, could cause the file to be slightly corrupted and unreadable. (#147) - Fixed problems with reading "non-standard" FITS files with primary headers containing SIMPLE = F. PyFITS has never made many guarantees as to how such files are handled. But it should at least be possible to read their headers, and the data if possible. Saving changes to such a file should not try to prepend an unwanted valid PRIMARY HDU. (#157) - Fixed a bug where opening an image with ``disable_image_compression = True`` caused compression to be disabled for all subsequent ``pyfits.open()`` calls. (r1651) 3.0.7 (2012-04-10) ------------------ Changes in Behavior ^^^^^^^^^^^^^^^^^^^ - Slices of GroupData objects now return new GroupData objects instead of extended multi-row _Group objects. This is analogous to how PyFITS 3.0 fixed FITS_rec slicing, and should have been fixed for GroupData at the same time. The old behavior caused bugs where functions internal to Numpy expected that slicing an ndarray would return a new ndarray. As this is a rare usecase with a rare feature most users are unlikely to be affected by this change. - The previously internal _Group object for representing individual group records in a GroupData object are renamed Group and are now a public interface. However, there's almost no good reason to create Group objects directly, so it shouldn't be considered a "new feature". - An annoyance from PyFITS 3.0.6 was fixed, where the value of the EXTEND keyword was always being set to F if there are not actually any extension HDUs. It was unnecessary to modify this value. Bug Fixes ^^^^^^^^^ - Fixed GroupData objects to return new GroupData objects when sliced instead of _Group record objects. See "Changes in behavior" above for more details. - Fixed slicing of Group objects--previously it was not possible to slice slice them at all. - Made it possible to assign `np.bool_` objects as header values. (#123) - Fixed overly strict handling of the EXTEND keyword; see "Changes in behavior" above. (#124) - Fixed many cases where an HDU's header would be marked as "modified" by PyFITS and rewritten, even when no changes to the header are necessary. (#125) - Fixed a bug where the values of the PTYPEn keywords in a random groups HDU were forced to be all lower-case when saving the file. (#130) - Removed an unnecessary inline import in `ExtensionHDU.__setattr__` that was causing some slowdown when opening files containing a large number of extensions, plus a few other small (but not insignficant) performance improvements thanks to Julian Taylor. (#133) - Fixed a regression where header blocks containing invalid end-of-header padding (i.e. null bytes instead of spaces) couldn't be parsed by PyFITS. Such headers can be parsed again, but a warning is raised, as such headers are not valid FITS. (#136) - Fixed a memory leak where table data in random groups HDUs weren't being garbage collected. (#138) 3.0.6 (2012-02-29) ------------------ Highlights ^^^^^^^^^^ The main reason for this release is to fix an issue that was introduced in PyFITS 3.0.5 where merely opening a file containing scaled data (that is, with non-trivial BSCALE and BZERO keywords) in 'update' mode would cause the data to be automatically rescaled--possibly converting the data from ints to floats--as soon as the file is closed, even if the application did not touch the data. Now PyFITS will only rescale the data in an extension when the data is actually accessed by the application. So opening a file in 'update' mode in order to modify the header or append new extensions will not cause any change to the data in existing extensions. This release also fixes a few Windows-specific bugs found through more extensive Windows testing, and other miscellaneous bugs. Bug Fixes ^^^^^^^^^ - More accurate error messages when opening files containing invalid header cards. (#109) - Fixed a possible reference cycle/memory leak that was caught through more extensive testing on Windows. (#112) - Fixed 'ostream' mode to open the underlying file in 'wb' mode instead of 'w' mode. (#112) - Fixed a Windows-only issue where trying to save updates to a resized FITS file could result in a crash due to there being open mmaps on that file. (#112) - Fixed a crash when trying to create a FITS table (i.e. with new_table()) from a Numpy array containing bool fields. (#113) - Fixed a bug where manually initializing an ``HDUList`` with a list of of HDUs wouldn't set the correct EXTEND keyword value on the primary HDU. (#114) - Fixed a crash that could occur when trying to deepcopy a Header in Python < 2.7. (#115) - Fixed an issue where merely opening a scaled image in 'update' mode would cause the data to be converted to floats when the file is closed. (#119) 3.0.5 (2012-01-30) ------------------ - Fixed a crash that could occur when accessing image sections of files opened with memmap=True. (r1211) - Fixed the inconsistency in the behavior of files opened in 'readonly' mode when memmap=True vs. when memmap=False. In the latter case, although changes to array data were not saved to disk, it was possible to update the array data in memory. On the other hand with memmap=True, 'readonly' mode prevented even in-memory modification to the data. This is what 'copyonwrite' mode was for, but difference in behavior was confusing. Now 'readonly' is equivalent to 'copyonwrite' when using memmap. If the old behavior of denying changes to the array data is necessary, a new 'denywrite' mode may be used, though it is only applicable to files opened with memmap. (r1275) - Fixed an issue where files opened with memmap=True would return image data as a raw numpy.memmap object, which can cause some unexpected behaviors--instead memmap object is viewed as a numpy.ndarray. (r1285) - Fixed an issue in Python 3 where a workaround for a bug in Numpy on Python 3 interacted badly with some other software, namely to vo.table package (and possibly others). (r1320, r1337, and #110) - Fixed buggy behavior in the handling of SIGINTs (i.e. Ctrl-C keyboard interrupts) while flushing changes to a FITS file. PyFITS already prevented SIGINTs from causing an incomplete flush, but did not clean up the signal handlers properly afterwards, or reraise the keyboard interrupt once the flush was complete. (r1321) - Fixed a crash that could occur in Python 3 when opening files with checksum checking enabled. (r1336) - Fixed a small bug that could cause a crash in the `StreamingHDU` interface when using Numpy below version 1.5. - Fixed a crash that could occur when creating a new `CompImageHDU` from an array of big-endian data. (#104) - Fixed a crash when opening a file with extra zero padding at the end. Though FITS files should not have such padding, it's not explictly forbidden by the format either, and PyFITS shouldn't stumble over it. (#106) - Fixed a major slowdown in opening tables containing large columns of string values. (#111) 3.0.4 (2011-11-22) ------------------ - Fixed a crash when writing HCOMPRESS compressed images that could happen on Python 2.5 and 2.6. (r1217) - Fixed a crash when slicing an table in a file opened in 'readonly' mode with memmap=True. (r1230) - Writing changes to a file or writing to a new file verifies the output in 'fix' mode by default instead of 'exception'--that is, PyFITS will automatically fix common FITS format errors rather than raising an exception. (r1243) - Fixed a bug where convenience functions such as getval() and getheader() crashed when specifying just 'PRIMARY' as the extension to use (r1263). - Fixed a bug that prevented passing keyword arguments (beyond the standard data and header arguments) as positional arguments to the constructors of extension HDU classes. - Fixed some tests that were failing on Windows--in this case the tests themselves failed to close some temp files and Windows refused to delete them while there were still open handles on them. (r1295) - Fixed an issue with floating point formatting in header values on Python 2.5 for Windows (and possibly other platforms). The exponent was zero-padded to 3 digits; although the FITS standard makes no specification on this, the formatting is now normalized to always pad the exponent to two digits. (r1295) - Fixed a bug where long commentary cards (such as HISTORY and COMMENT) were broken into multiple CONTINUE cards. However, commentary cards are not expected to be found in CONTINUE cards. Instead these long cards are broken into multiple commentary cards. (#97) - GZIP/ZIP-compressed FITS files can be detected and opened regardless of their filename extension. (#99) - Fixed a serious bug where opening scaled images in 'update' mode and then closing the file without touching the data would cause the file to be corrupted. (#101) 3.0.3 (2011-10-05) ------------------ - Fixed several small bugs involving corner cases in record-valued keyword cards (#70) - In some cases HDU creation failed if the first keyword value in the header was not a string value (#89) - Fixed a crash when trying to compute the HDU checksum when the data array contains an odd number of bytes (#91) - Disabled an unnecessary warning that was displayed on opening compressed HDUs with disable_image_compression = True (#92) - Fixed a typo in code for handling HCOMPRESS compressed images. 3.0.2 (2011-09-23) ------------------ - The ``BinTableHDU.tcreate`` method and by extension the ``pyfits.tcreate`` function don't get tripped up by blank lines anymore (#14) - The presence, value, and position of the EXTEND keyword in Primary HDUs is verified when reading/writing a FITS file (#32) - Improved documentation (in warning messages as well as in the handbook) that PyFITS uses zero-based indexing (as one would expect for C/Python code, but contrary to the PyFITS standard which was written with FORTRAN in mind) (#68) - Fixed a bug where updating a header card comment could cause the value to be lost if it had not already been read from the card image string. - Fixed a related bug where changes made directly to Card object in a header (i.e. assigning directly to card.value or card.comment) would not propagate when flushing changes to the file (#69) [Note: This and the bug above it were originally reported as being fixed in version 3.0.1, but the fix was never included in the release.] - Improved file handling, particularly in Python 3 which had a few small file I/O-related bugs (#76) - Fixed a bug where updating a FITS file would sometimes cause it to lose its original file permissions (#79) - Fixed the handling of TDIMn keywords; 3.0 added support for them, but got the axis order backards (they were treated as though they were row-major) (#82) - Fixed a crash when a FITS file containing scaled data is opened and immediately written to a new file without explicitly viewing the data first (#84) - Fixed a bug where creating a table with columns named either 'names' or 'formats' resulted in an infinite recursion (#86) 3.0.1 (2011-09-12) ------------------ - Fixed a bug where updating a header card comment could cause the value to be lost if it had not already been read from the card image string. - Changed ``_TableBaseHDU.data`` so that if the data contain an empty table a ``FITS_rec`` object with zero rows is returned rather than ``None``. - The ``.key`` attribute of ``RecordValuedKeywordCards`` now returns the full keyword+field-specifier value, instead of just the plain keyword (#46) - Fixed a related bug where changes made directly to Card object in a header (i.e. assigning directly to card.value or card.comment) would not propagate when flushing changes to the file (#69) - Fixed a bug where writing a table with zero rows could fail in some cases (#72) - Miscellanous small bug fixes that were causing some tests to fail, particularly on Python 3 (#74, #75) - Fixed a bug where creating a table column from an array in non-native byte order would not preserve the byte order, thus interpreting the column array using the wrong byte order (#77) 3.0.0 (2011-08-23) -------------------- - Contains major changes, bumping the version to 3.0 - Large amounts of refactoring and reorganization of the code; tried to preserve public API backwards-compatibility with older versions (private API has many changes and is not guaranteed to be backwards-compatible). There are a few small public API changes to be aware of: * The pyfits.rec module has been removed completely. If your version of numpy does not have the numpy.core.records module it is too old to be used with PyFITS. * The ``Header.ascardlist()`` method is deprecated--use the ``.ascard`` attribute instead. * ``Card`` instances have a new ``.cardimage`` attribute that should be used rather than ``.ascardimage()``, which may become deprecated. * The ``Card.fromstring()`` method is now a classmethod. It returns a new ``Card`` instance rather than modifying an existing instance. * The ``req_cards()`` method on HDU instances has changed: The ``pos`` argument is not longer a string. It is either an integer value (meaning the card's position must match that value) or it can be a function that takes the card's position as it's argument, and returns True if the position is valid. Likewise, the ``test`` argument no longer takes a string, but instead a function that validates the card's value and returns True or False. * The ``get_coldefs()`` method of table HDUs is deprecated. Use the ``.columns`` attribute instead. * The ``ColDefs.data`` attribute is deprecated--use ``ColDefs.columns`` instead (though in general you shouldn't mess with it directly--it might become internal at some point). * ``FITS_record`` objects take ``start`` and ``end`` as arguments instead of ``startColumn`` and ``endColumn`` (these are rarely created manually, so it's unlikely that this change will affect anyone). * ``BinTableHDU.tcreate()`` is now a classmethod, and returns a new ``BinTableHDU`` instance. * Use ``ExtensionHDU`` and ``NonstandardExtHDU`` for making new extension HDU classes. They are now public interfaces, wheres previously they were private and prefixed with underscores. * Possibly others--please report if you find any changes that cause difficulties. - Calls to deprecated functions will display a Deprecation warning. However, in Python 2.7 and up Deprecation warnings are ignored by default, so run Python with the `-Wd` option to see if you're using any deprecated functions. If we get close to actually removing any functions, we might make the Deprecation warnings display by default. - Added basic Python 3 support - Added support for multi-dimensional columns in tables as specified by the TDIMn keywords (#47) - Fixed a major memory leak that occurred when creating new tables with the ``new_table()`` function (#49) be padded with zero-bytes) vs ASCII tables (where strings are padded with spaces) (#15) - Fixed a bug in which the case of Random Access Group parameters names was not preserved when writing (#41) - Added support for binary table fields with zero width (#42) - Added support for wider integer types in ASCII tables; although this is non- standard, some GEIS images require it (#45) - Fixed a bug that caused the index_of() method of HDULists to crash when the HDUList object is created from scratch (#48) - Fixed the behavior of string padding in binary tables (where strings should be padded with nulls instead of spaces) - Fixed a rare issue that caused excessive memory usage when computing checksums using a non-standard block size (see r818) - Add support for forced uint data in image sections (#53) - Fixed an issue where variable-length array columns were not extended when creating a new table with more rows than the original (#54) - Fixed tuple and list-based indexing of FITS_rec objects (#55) - Fixed an issue where BZERO and BSCALE keywords were appended to headers in the wrong location (#56) - ``FITS_record`` objects (table rows) have full slicing support, including stepping, etc. (#59) - Fixed a bug where updating multiple files simultaneously (such as when running parallel processes) could lead to a race condition with mktemp() (#61) - Fixed a bug where compressed image headers were not in the order expected by the funpack utility (#62)
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FITS (Flexible Image Transport System) is a data format most used in astronomy.
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PyFITS is a Python module for reading, writing, and manipulating FITS files.
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The module uses Python's object-oriented features to provide quick, easy, and
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efficient access to FITS files. The use of Python's array syntax enables
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immediate access to any FITS extension, header cards, or data items.
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