def update(self, func, default=None, testing_value=None,
missing_values=asbytes(''), locked=False):
"""
Set StringConverter attributes directly.
Parameters
----------
func : function
Conversion function.
default : any, optional
Value to return by default, that is, when the string to be
converted is flagged as missing. If not given,
`StringConverter` tries to supply a reasonable default value.
testing_value : str, optional
A string representing a standard input value of the converter.
This string is used to help defining a reasonable default
value.
missing_values : sequence of str, optional
Sequence of strings indicating a missing value.
locked : bool, optional
Whether the StringConverter should be locked to prevent
automatic upgrade or not. Default is False.
Notes
-----
`update` takes the same parameters as the constructor of
`StringConverter`, except that `func` does not accept a `dtype`
whereas `dtype_or_func` in the constructor does.
"""
self.func = func
self._locked = locked
# Don't reset the default to None if we can avoid it
if default is not None:
self.default = default
self.type = self._dtypeortype(self._getdtype(default))
else:
try:
tester = func(testing_value or asbytes('1'))
except (TypeError, ValueError):
tester = None
self.type = self._dtypeortype(self._getdtype(tester))
# Add the missing values to the existing set
if missing_values is not None:
if _is_bytes_like(missing_values):
self.missing_values.add(missing_values)
elif hasattr(missing_values, '__iter__'):
for val in missing_values:
self.missing_values.add(val)
else:
self.missing_values = []
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