Cannot read some non-standard FITS files

I’m trying to read a fits file and get its header and contents, but no matter what I do astropy gives me errors:

with fits.open(Path('J0721+7120_C_2014_02_18_pet_vis.fits').open('rb')) as f:
    f['PRIMARY'].header['RA']

---------------------------------------------------------------------------
VerifyError                               Traceback (most recent call last)
<ipython-input-44-e7947a571936> in <module>
      1 with fits.open(Path('J0721+7120_C_2014_02_18_pet_vis.fits').open('rb')) as f:
----> 2     f['PRIMARY'].header['RA']

~/anaconda3/lib/python3.7/site-packages/astropy/io/fits/header.py in __getitem__(self, key)
    152             return card.rawvalue
    153 
--> 154         value = card.value
    155         if value == UNDEFINED:
    156             return None

~/anaconda3/lib/python3.7/site-packages/astropy/io/fits/card.py in value(self)
    283             value = self._value
    284         elif self._valuestring is not None or self._image:
--> 285             value = self._value = self._parse_value()
    286         else:
    287             if self._keyword == '':

~/anaconda3/lib/python3.7/site-packages/astropy/io/fits/card.py in _parse_value(self)
    765         if m is None:
    766             raise VerifyError("Unparsable card ({}), fix it first with "
--> 767                               ".verify('fix').".format(self.keyword))
    768 
    769         if m.group('bool') is not None:

VerifyError: Unparsable card (RA), fix it first with .verify('fix').

with fits.open(Path('J0721+7120_C_2014_02_18_pet_vis.fits').open('rb')) as f:
    f.verify('fix')

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-43-ed0088ff4893> in <module>
      1 with fits.open(Path('J0721+7120_C_2014_02_18_pet_vis.fits').open('rb')) as f:
----> 2     f.verify('fix')

~/anaconda3/lib/python3.7/site-packages/astropy/io/fits/verify.py in verify(self, option)
     71             return
     72 
---> 73         errs = self._verify(opt)
     74 
     75         # Break the verify option into separate options related to reporting of

~/anaconda3/lib/python3.7/site-packages/astropy/io/fits/hdu/hdulist.py in _verify(self, option)
   1191 
   1192         # the first (0th) element must be a primary HDU
-> 1193         if len(self) > 0 and (not isinstance(self[0], PrimaryHDU)) and \
   1194                              (not isinstance(self[0], _NonstandardHDU)):
   1195             err_text = "HDUList's 0th element is not a primary HDU."

~/anaconda3/lib/python3.7/site-packages/astropy/io/fits/hdu/hdulist.py in __len__(self)
    226     def __len__(self):
    227         if not self._in_read_next_hdu:
--> 228             self.readall()
    229 
    230         return super().__len__()

~/anaconda3/lib/python3.7/site-packages/astropy/io/fits/hdu/hdulist.py in readall(self)
    767         Read data of all HDUs into memory.
    768         """
--> 769         while self._read_next_hdu():
    770             pass
    771 

~/anaconda3/lib/python3.7/site-packages/astropy/io/fits/hdu/hdulist.py in _read_next_hdu(self)
   1137                                 fileobj.seek(offset, os.SEEK_SET)
   1138 
-> 1139                         hdu = _BaseHDU.readfrom(fileobj, **kwargs)
   1140                     except EOFError:
   1141                         self._read_all = True

~/anaconda3/lib/python3.7/site-packages/astropy/io/fits/hdu/base.py in readfrom(cls, fileobj, checksum, ignore_missing_end, **kwargs)
    326         hdu = cls._readfrom_internal(fileobj, checksum=checksum,
    327                                      ignore_missing_end=ignore_missing_end,
--> 328                                      **kwargs)
    329 
    330         # If the checksum had to be checked the data may have already been read

~/anaconda3/lib/python3.7/site-packages/astropy/io/fits/hdu/base.py in _readfrom_internal(cls, data, header, checksum, ignore_missing_end, **kwargs)
    462                     del new_kwargs[key]
    463 
--> 464         hdu = cls(data=DELAYED, header=header, **new_kwargs)
    465 
    466         # One of these may be None, depending on whether the data came from a

~/anaconda3/lib/python3.7/site-packages/astropy/io/fits/hdu/table.py in __init__(self, data, header, name, uint, ver, character_as_bytes)
    851 
    852         super().__init__(data, header, name=name, uint=uint, ver=ver,
--> 853                          character_as_bytes=character_as_bytes)
    854 
    855     @classmethod

~/anaconda3/lib/python3.7/site-packages/astropy/io/fits/hdu/table.py in __init__(self, data, header, name, uint, ver, character_as_bytes)
    370         if not (isinstance(self._header[0], str) and
    371                 self._header[0].rstrip() == self._extension):
--> 372             self._header[0] = (self._extension, self._ext_comment)
    373 
    374         # Ensure that the correct EXTNAME is set on the new header if one was

TypeError: '_BasicHeader' object does not support item assignment

The example file can be downloaded from http://astrogeo.org/images/J0721+7120/J0721+7120_C_2014_02_18_pet_vis.fits.

astropy.__version__ = '3.2.1'

[aplavin]

Thanks a lot for that prompt response and fix! I installed latest astropy by running pip install git+https://github.com/astropy/astropy and it can read all the files from that dataset.

[saimn]

@aplavin - See #9012 for a proposed fix.