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ENH: Allow dict as the argument to Index.map (GH13517) #13518

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ENH: Allow dict as the argument to Index.map (GH13517) #13518

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2a67719
ENH: Allow dict as the argument to Index.map (GH13517)
evanpw Jun 26, 2016
e82dc92
Allow for dict-like mappers that are not dicts, and for missing values
evanpw Jun 26, 2016
0b32709
Split too-long line
evanpw Jun 26, 2016
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1 change: 1 addition & 0 deletions doc/source/whatsnew/v0.18.2.txt
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Expand Up @@ -207,6 +207,7 @@ Other enhancements
- The ``pd.read_csv()`` with ``engine='python'`` has gained support for the ``na_filter`` option (:issue:`13321`)
- The ``pd.read_csv()`` with ``engine='python'`` has gained support for the ``memory_map`` option (:issue:`13381`)

- ``Index.map`` now accepts a dictionary as its argument (:issue:`13517`)
- ``Index.astype()`` now accepts an optional boolean argument ``copy``, which allows optional copying if the requirements on dtype are satisfied (:issue:`13209`)
- ``Index`` now supports the ``.where()`` function for same shape indexing (:issue:`13170`)

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7 changes: 5 additions & 2 deletions pandas/indexes/base.py
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Expand Up @@ -2295,14 +2295,17 @@ def map(self, mapper):

Parameters
----------
mapper : callable
mapper : callable or dict
Function to be applied.

Returns
-------
applied : array
"""
return self._arrmap(self.values, mapper)
if isinstance(mapper, dict):
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is_dict_like covers a wider range of mappings

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Good point. Fixed.

return self._arrmap(self.values, lambda key: mapper[key])
else:
return self._arrmap(self.values, mapper)

def isin(self, values, level=None):
"""
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12 changes: 11 additions & 1 deletion pandas/tests/indexes/test_base.py
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Expand Up @@ -20,7 +20,7 @@
Float64Index, Int64Index,
CategoricalIndex, DatetimeIndex, TimedeltaIndex,
PeriodIndex)
from pandas.util.testing import assert_almost_equal
from pandas.util.testing import assert_almost_equal, assert_numpy_array_equal
from pandas.compat.numpy import np_datetime64_compat

import pandas.core.config as cf
Expand Down Expand Up @@ -1462,6 +1462,16 @@ def test_conversion_preserves_name(self):
self.assertEqual(i.name, pd.to_datetime(i).name)
self.assertEqual(i.name, pd.to_timedelta(i).name)

def test_map_dict(self):
# GH 13517
i = pd.Index(['a', 'b', 'c', 'd'])
d = {'a': 0, 'b': 2, 'c': 1, 'd': 5}

actual = i.map(d)
expected = np.array([0, 2, 1, 5])

tm.assert_numpy_array_equal(actual, expected)

def test_string_index_repr(self):
# py3/py2 repr can differ because of "u" prefix
# which also affects to displayed element size
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