Exception in loadarff with quoted nominal attributes in scipy 1.3.0

[sebp]

In scipy 1.3.0, loadarff has undergone some refactoring (see #9854), which breaks parsing ARFF files where nominal attributes are in quotes. I believe this is due to using csv.reader to parse individual lines, which does strip quotes, whereas NominalAttribute._get_nom_val preserves quotes.

Reproducing code example:

from scipy.io.arff import loadarff
from io import StringIO

ARFF_FILE = """@relation SOME_DATA
@attribute age numeric
@attribute smoker {'yes', 'no'}
@data
18,'no'
24,'yes'
44,'no'
56,'no'
89,'yes'
11,'no'
"""

with StringIO(ARFF_FILE) as fin:
    data, meta = loadarff(fin)

Error message:

Traceback (most recent call last):
  File "test_parse_nominal.py", line 18, in <module>
    loadarff(fin)
  File "/miniconda3/envs/scipy13/lib/python3.7/site-packages/scipy/io/arff/arffread.py", line 738, in loadarff
    return _loadarff(ofile)
  File "/miniconda3/envs/scipy13/lib/python3.7/site-packages/scipy/io/arff/arffread.py", line 803, in _loadarff
    a = list(generator(ofile))
  File "/miniconda3/envs/scipy13/lib/python3.7/site-packages/scipy/io/arff/arffread.py", line 801, in generator
    yield tuple([attr[i].parse_data(row[i]) for i in elems])
  File "/miniconda3/envs/scipy13/lib/python3.7/site-packages/scipy/io/arff/arffread.py", line 801, in <listcomp>
    yield tuple([attr[i].parse_data(row[i]) for i in elems])
  File "/miniconda3/envs/scipy13/lib/python3.7/site-packages/scipy/io/arff/arffread.py", line 165, in parse_data
    str(self.values)))
ValueError: no value not in ("'yes'", "'no'")

Note that the first no is the value to be parsed (using %r instead of %s might be a good idea).

Scipy/Numpy/Python version information:

1.3.0 1.16.4 sys.version_info(major=3, minor=7, micro=3, releaselevel='final', serial=0)

[rgommers]

Thanks for the report and reproducer @sebp.

@vnmabus would you be able to look into this?

[vnmabus]

I will look into this.

[vnmabus]

I have made the PR #10233 to correct this. Now, if the nominal attributes are quoted, the quotes are no longer considered part of the name.