def guess_colspec(otpl_reader):
"""
Note that for guessing to work, the optionally present global enumeration
column must be placed *before* the (also optional) local enumeration
column.
If the input file has a colspec header, that header is used instead of any
guessing.
:param otpl_reader: a reader instance
:type otpl_reader: OtplReader
:raises AttributeError: if the reader has an undefined separator property
:returns: a :class:`ColumnSpecification` or ``None`` if the guessing fails
"""
try:
guess = _make_guess(otpl_reader)
except (IOError, UnicodeDecodeError, DataFormatError) as e:
L.warning(str(e))
guess = []
if isinstance(guess, Spec):
L.info(u'from header: %s', str(guess))
return guess
elif len(guess) < 2:
L.warning(u'failed for "%s"', otpl_reader.path)
L.debug(u'discarded guess was: %s', Spec.to_string(guess))
return None
else:
L.debug(u'as: %s', Spec.to_string(guess))
return Spec.from_integers(guess)
