Writing simple ASCII tables broken with Numpy dev

In the last day or so I’ve started to see the following issue with the latest developer version of Numpy:

In [2]: from astropy.table import Table

In [3]: t = Table()

In [4]: t['a'] = [1,2,3]

In [5]: t['b'] = ['a', 'b', 'c']

In [6]: t.write('test.tex', format='ascii.latex')
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-6-b9a1187ff345> in <module>()
----> 1 t.write('test.tex', format='ascii.latex')

~/miniconda3/envs/glue-dev/lib/python3.6/site-packages/astropy/table/table.py in write(self, *args, **kwargs)
   2548         passed through to the underlying data reader (e.g. `~astropy.io.ascii.write`).
   2549         """
-> 2550         io_registry.write(self, *args, **kwargs)
   2551 
   2552     def copy(self, copy_data=True):

~/miniconda3/envs/glue-dev/lib/python3.6/site-packages/astropy/io/registry.py in write(data, *args, **kwargs)
    579 
    580     writer = get_writer(format, data.__class__)
--> 581     writer(data, *args, **kwargs)
    582 
    583 

~/miniconda3/envs/glue-dev/lib/python3.6/site-packages/astropy/io/ascii/connect.py in io_write(format, table, filename, **kwargs)
     43     from .ui import write
     44     format = re.sub(r'^ascii\.', '', format)
---> 45     return write(table, filename, format=format, **kwargs)
     46 
     47 

~/miniconda3/envs/glue-dev/lib/python3.6/site-packages/astropy/io/ascii/ui.py in write(table, output, format, Writer, fast_writer, **kwargs)
    733         return
    734 
--> 735     lines = writer.write(table)
    736 
    737     # Write the lines to output

~/miniconda3/envs/glue-dev/lib/python3.6/site-packages/astropy/io/ascii/latex.py in write(self, table)
    329         self.header.start_line = None
    330         self.data.start_line = None
--> 331         return core.BaseReader.write(self, table=table)
    332 
    333 

~/miniconda3/envs/glue-dev/lib/python3.6/site-packages/astropy/io/ascii/core.py in write(self, table)
   1311         lines = []
   1312         self.write_header(lines, table.meta)
-> 1313         self.data.write(lines)
   1314 
   1315         return lines

~/miniconda3/envs/glue-dev/lib/python3.6/site-packages/astropy/io/ascii/latex.py in write(self, lines)
    181     def write(self, lines):
    182         add_dictval_to_list(self.latex, 'data_start', lines)
--> 183         core.BaseData.write(self, lines)
    184         add_dictval_to_list(self.latex, 'data_end', lines)
    185         lines.append(self.data_end)

~/miniconda3/envs/glue-dev/lib/python3.6/site-packages/astropy/io/ascii/core.py in write(self, lines)
    829             lines.append(itertools.cycle(self.write_spacer_lines))
    830 
--> 831         col_str_iters = self.str_vals()
    832         for vals in zip(*col_str_iters):
    833             lines.append(self.splitter.join(vals))

~/miniconda3/envs/glue-dev/lib/python3.6/site-packages/astropy/io/ascii/core.py in str_vals(self)
    813     def str_vals(self):
    814         '''convert all values in table to a list of lists of strings'''
--> 815         self._set_fill_values(self.cols)
    816         self._set_col_formats()
    817         for col in self.cols:

~/miniconda3/envs/glue-dev/lib/python3.6/site-packages/astropy/io/ascii/core.py in _set_fill_values(self, cols)
    787                 for i, key in ((i, x) for i, x in enumerate(self.header.colnames)
    788                                if x in affect_cols):
--> 789                     cols[i].fill_values[replacement[0]] = str(replacement[1])
    790 
    791     def _set_masks(self, cols):

TypeError: unhashable type: 'MaskedConstant'

I’ll try and bisect.

[mhvk]

This should be fixed by https://github.com/numpy/numpy/pull/9822 (thanks, @eric-wieser!), so I’ll close the issue.

[astrofrog]

Also cc @mhvk since you seem to enjoy these kinds of issues 😃