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Improve error messages for unit conversion #13005

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Merged
timhoffm merged 1 commit into from
Jan 12, 2019
Merged

Improve error messages for unit conversion #13005

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7 changes: 5 additions & 2 deletions lib/matplotlib/axis.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1486,8 +1486,11 @@ def convert_units(self, x):

if self.converter is None:
return x

ret = self.converter.convert(x, self.units, self)
try:
ret = self.converter.convert(x, self.units, self)
except Exception as e:
raise munits.ConversionError('Failed to convert value(s) to axis '
f'units: {x!r}') from e
return ret

def set_units(self, u):
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26 changes: 16 additions & 10 deletions lib/matplotlib/category.py
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Expand Up @@ -23,24 +23,30 @@
class StrCategoryConverter(units.ConversionInterface):
@staticmethod
def convert(value, unit, axis):
"""Converts strings in value to floats using
"""Convert strings in value to floats using

@anntzer anntzer Jan 11, 2019

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Just inherit the docstring from units.ConversionInterface perhaps? (and possibly edit that docstring).

@timhoffm timhoffm Jan 12, 2019

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I don't think we can reasonably use an inherited docstring here. Using the conversion interface for string-index mapping is a bit of a stretch and justifies explicit description.

  • type of value is a string, which is rather the exception for ConversionInterface
  • mark unit as UnitData
  • note that axis is unused.

@anntzer anntzer Jan 12, 2019

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sure

mapping information store in the unit object.

Parameters
----------
value : string or iterable
value or list of values to be converted
unit : :class:`.UnitData`
object string unit information for value
axis : :class:`~matplotlib.Axis.axis`
axis on which the converted value is plotted
Value or list of values to be converted.
unit : `.UnitData`
An object mapping strings to integers.
axis : `~matplotlib.axis.Axis`
axis on which the converted value is plotted.

.. note:: *axis* is unused.

Returns
-------
mapped_ value : float or ndarray[float]

.. note:: axis is not used in this function
mapped_value : float or ndarray[float]
"""
if unit is None:
raise ValueError(
'Missing category information for StrCategoryConverter; '
'this might be caused by unintendedly mixing categorical and '
'numeric data')

# dtype = object preserves numerical pass throughs
values = np.atleast_1d(np.array(value, dtype=object))

Expand Down Expand Up @@ -190,7 +196,7 @@ def update(self, data):
self._mapping[val] = next(self._counter)


# Connects the convertor to matplotlib
# Register the converter with Matplotlib's unit framework
units.registry[str] = StrCategoryConverter()
units.registry[np.str_] = StrCategoryConverter()
units.registry[bytes] = StrCategoryConverter()
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4 changes: 4 additions & 0 deletions lib/matplotlib/units.py
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Expand Up @@ -49,6 +49,10 @@ def default_units(x, axis):
from matplotlib import cbook


class ConversionError(TypeError):
pass


class AxisInfo(object):
"""
Information to support default axis labeling, tick labeling, and
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