ENH: Add dtype parameter to IntervalIndex constructors and deprecate from_intervals

doc/source/api.rst

@@ -1617,7 +1617,6 @@ IntervalIndex Components
    IntervalIndex.from_arrays
    IntervalIndex.from_tuples
    IntervalIndex.from_breaks
-   IntervalIndex.from_intervals
    IntervalIndex.contains
    IntervalIndex.left
    IntervalIndex.right

doc/source/whatsnew/v0.23.0.txt

@@ -207,9 +207,8 @@ Other Enhancements
   :func:`pandas.api.extensions.register_index_accessor`, accessor for libraries downstream of pandas
   to register custom accessors like ``.cat`` on pandas objects. See
   :ref:`Registering Custom Accessors <developer.register-accessors>` for more (:issue:`14781`).
-
-
 - ``IntervalIndex.astype`` now supports conversions between subtypes when passed an ``IntervalDtype`` (:issue:`19197`)
+- :class:`IntervalIndex` and its associated constructor methods (``from_arrays``, ``from_breaks``, ``from_tuples``) have gained a ``dtype`` parameter (:issue:`19262`)
 
 .. _whatsnew_0230.api_breaking:
 
@@ -329,6 +328,7 @@ Deprecations
 - ``Series.valid`` is deprecated. Use :meth:`Series.dropna` instead (:issue:`18800`).
 - :func:`read_excel` has deprecated the ``skip_footer`` parameter. Use ``skipfooter`` instead (:issue:`18836`)
 - The ``is_copy`` attribute is deprecated and will be removed in a future version (:issue:`18801`).
+- ``IntervalIndex.from_intervals`` is deprecated in favor of the :class:`IntervalIndex` constructor (:issue:`19263`)
 
 
 .. _whatsnew_0230.prior_deprecations:

pandas/core/indexes/base.py

@@ -200,7 +200,9 @@ def __new__(cls, data=None, dtype=None, copy=False, name=None,
         # interval
         if is_interval_dtype(data) or is_interval_dtype(dtype):
             from .interval import IntervalIndex
-            return IntervalIndex(data, dtype=dtype, name=name, copy=copy)
+            closed = kwargs.get('closed', None)
+            return IntervalIndex(data, dtype=dtype, name=name, copy=copy,
+                                 closed=closed)
 
         # index-like
         elif isinstance(data, (np.ndarray, Index, ABCSeries)):
@@ -313,8 +315,7 @@ def __new__(cls, data=None, dtype=None, copy=False, name=None,
                     return Float64Index(subarr, copy=copy, name=name)
                 elif inferred == 'interval':
                     from .interval import IntervalIndex
-                    return IntervalIndex.from_intervals(subarr, name=name,
-                                                        copy=copy)
+                    return IntervalIndex(subarr, name=name, copy=copy)
                 elif inferred == 'boolean':
                     # don't support boolean explicitly ATM
                     pass

pandas/core/indexes/category.py

@@ -341,7 +341,7 @@ def __array__(self, dtype=None):
     def astype(self, dtype, copy=True):
         if is_interval_dtype(dtype):
             from pandas import IntervalIndex
-            return IntervalIndex.from_intervals(np.array(self))
+            return IntervalIndex(np.array(self))
         elif is_categorical_dtype(dtype):
             # GH 18630
             dtype = self.dtype._update_dtype(dtype)

pandas/core/indexes/interval.py

@@ -1,6 +1,7 @@
 """ define the IntervalIndex """
 
 import numpy as np
+import warnings
 
 from pandas.core.dtypes.missing import notna, isna
 from pandas.core.dtypes.generic import ABCDatetimeIndex, ABCPeriodIndex
@@ -151,6 +152,10 @@ class IntervalIndex(IntervalMixin, Index):
         Name to be stored in the index.
     copy : boolean, default False
         Copy the meta-data
+    dtype : dtype or None, default None
+        If None, dtype will be inferred
+
+        ..versionadded:: 0.23.0
 
     Attributes
     ----------
@@ -167,7 +172,6 @@ class IntervalIndex(IntervalMixin, Index):
     from_arrays
     from_tuples
     from_breaks
-    from_intervals
     contains
 
     Examples
@@ -181,8 +185,7 @@ class IntervalIndex(IntervalMixin, Index):
 
     It may also be constructed using one of the constructor
     methods: :meth:`IntervalIndex.from_arrays`,
-    :meth:`IntervalIndex.from_breaks`, :meth:`IntervalIndex.from_intervals`
-    and :meth:`IntervalIndex.from_tuples`.
+    :meth:`IntervalIndex.from_breaks`, and :meth:`IntervalIndex.from_tuples`.
 
     See further examples in the doc strings of ``interval_range`` and the
     mentioned constructor methods.
@@ -211,8 +214,7 @@ class IntervalIndex(IntervalMixin, Index):
 
     _mask = None
 
-    def __new__(cls, data, closed=None,
-                name=None, copy=False, dtype=None,
+    def __new__(cls, data, closed=None, name=None, copy=False, dtype=None,
                 fastpath=False, verify_integrity=True):
 
         if fastpath:
@@ -245,19 +247,28 @@ def __new__(cls, data, closed=None,
 
             closed = closed or infer_closed
 
-        return cls._simple_new(left, right, closed, name,
-                               copy=copy, verify_integrity=verify_integrity)
+        return cls._simple_new(left, right, closed, name, copy=copy,
+                               dtype=dtype, verify_integrity=verify_integrity)
 
     @classmethod
-    def _simple_new(cls, left, right, closed=None, name=None,
-                    copy=False, verify_integrity=True):
+    def _simple_new(cls, left, right, closed=None, name=None, copy=False,
+                    dtype=None, verify_integrity=True):
         result = IntervalMixin.__new__(cls)
 
-        if closed is None:
-            closed = 'right'
+        closed = closed or 'right'
         left = _ensure_index(left, copy=copy)
         right = _ensure_index(right, copy=copy)
 
+        if dtype is not None:
+            # GH 19262: dtype must be an IntervalDtype to override inferred
+            dtype = pandas_dtype(dtype)
+            if not is_interval_dtype(dtype):
+                msg = 'dtype must be an IntervalDtype, got {dtype}'
+                raise TypeError(msg.format(dtype=dtype))
+            elif dtype.subtype is not None:
+                left = left.astype(dtype.subtype)
+                right = right.astype(dtype.subtype)
+
         # coerce dtypes to match if needed
         if is_float_dtype(left) and is_integer_dtype(right):
             right = right.astype(left.dtype)
@@ -304,7 +315,7 @@ def _shallow_copy(self, left=None, right=None, **kwargs):
             # only single value passed, could be an IntervalIndex
             # or array of Intervals
             if not isinstance(left, IntervalIndex):
-                left = type(self).from_intervals(left)
+                left = self._constructor(left)
 
             left, right = left.left, left.right
         else:
@@ -322,7 +333,7 @@ def _validate(self):
         Verify that the IntervalIndex is valid.
         """
         if self.closed not in _VALID_CLOSED:
-            raise ValueError("invalid options for 'closed': {closed}"
+            raise ValueError("invalid option for 'closed': {closed}"
                              .format(closed=self.closed))
         if len(self.left) != len(self.right):
             raise ValueError('left and right must have the same length')
@@ -356,7 +367,7 @@ def _engine(self):
 
     @property
     def _constructor(self):
-        return type(self).from_intervals
+        return type(self)
 
     def __contains__(self, key):
         """
@@ -402,7 +413,8 @@ def contains(self, key):
             return False
 
     @classmethod
-    def from_breaks(cls, breaks, closed='right', name=None, copy=False):
+    def from_breaks(cls, breaks, closed='right', name=None, copy=False,
+                    dtype=None):
         """
         Construct an IntervalIndex from an array of splits
 
@@ -417,6 +429,10 @@ def from_breaks(cls, breaks, closed='right', name=None, copy=False):
             Name to be stored in the index.
         copy : boolean, default False
             copy the data
+        dtype : dtype or None, default None
+            If None, dtype will be inferred
+
+            ..versionadded:: 0.23.0
 
         Examples
         --------
@@ -430,18 +446,17 @@ def from_breaks(cls, breaks, closed='right', name=None, copy=False):
         interval_range : Function to create a fixed frequency IntervalIndex
         IntervalIndex.from_arrays : Construct an IntervalIndex from a left and
                                     right array
-        IntervalIndex.from_intervals : Construct an IntervalIndex from an array
-                                       of Interval objects
         IntervalIndex.from_tuples : Construct an IntervalIndex from a
                                     list/array of tuples
         """
         breaks = maybe_convert_platform_interval(breaks)
 
         return cls.from_arrays(breaks[:-1], breaks[1:], closed,
-                               name=name, copy=copy)
+                               name=name, copy=copy, dtype=dtype)
 
     @classmethod
-    def from_arrays(cls, left, right, closed='right', name=None, copy=False):
+    def from_arrays(cls, left, right, closed='right', name=None, copy=False,
+                    dtype=None):
         """
         Construct an IntervalIndex from a a left and right array
 
@@ -458,6 +473,10 @@ def from_arrays(cls, left, right, closed='right', name=None, copy=False):
             Name to be stored in the index.
         copy : boolean, default False
             copy the data
+        dtype : dtype or None, default None
+            If None, dtype will be inferred
+
+            ..versionadded:: 0.23.0
 
         Examples
         --------
@@ -471,22 +490,23 @@ def from_arrays(cls, left, right, closed='right', name=None, copy=False):
         interval_range : Function to create a fixed frequency IntervalIndex
         IntervalIndex.from_breaks : Construct an IntervalIndex from an array of
                                     splits
-        IntervalIndex.from_intervals : Construct an IntervalIndex from an array
-                                       of Interval objects
         IntervalIndex.from_tuples : Construct an IntervalIndex from a
                                     list/array of tuples
         """
         left = maybe_convert_platform_interval(left)
         right = maybe_convert_platform_interval(right)
 
-        return cls._simple_new(left, right, closed, name=name,
-                               copy=copy, verify_integrity=True)
+        return cls._simple_new(left, right, closed, name=name, copy=copy,
+                               dtype=dtype, verify_integrity=True)
 
     @classmethod
-    def from_intervals(cls, data, name=None, copy=False):
+    def from_intervals(cls, data, closed=None, name=None, copy=False,
+                       dtype=None):
         """
         Construct an IntervalIndex from a 1d array of Interval objects
 
+        .. deprecated:: 0.23.0
+
         Parameters
         ----------
         data : array-like (1-dimensional)
@@ -496,6 +516,10 @@ def from_intervals(cls, data, name=None, copy=False):
             Name to be stored in the index.
         copy : boolean, default False
             by-default copy the data, this is compat only and ignored
+        dtype : dtype or None, default None
+            If None, dtype will be inferred
+
+            ..versionadded:: 0.23.0
 
         Examples
         --------
@@ -521,16 +545,14 @@ def from_intervals(cls, data, name=None, copy=False):
         IntervalIndex.from_tuples : Construct an IntervalIndex from a
                                     list/array of tuples
         """
-        if isinstance(data, IntervalIndex):
-            left, right, closed = data.left, data.right, data.closed
-            name = name or data.name
-        else:
-            data = maybe_convert_platform_interval(data)
-            left, right, closed = intervals_to_interval_bounds(data)
-        return cls.from_arrays(left, right, closed, name=name, copy=False)
+        msg = ('IntervalIndex.from_intervals is deprecated and will be '
+               'removed in a future version; use IntervalIndex(...) instead')
+        warnings.warn(msg, FutureWarning, stacklevel=2)
+        return cls(data, closed=closed, name=name, copy=copy, dtype=dtype)
 
     @classmethod
-    def from_tuples(cls, data, closed='right', name=None, copy=False):
+    def from_tuples(cls, data, closed='right', name=None, copy=False,
+                    dtype=None):
         """
         Construct an IntervalIndex from a list/array of tuples
 
@@ -545,10 +567,14 @@ def from_tuples(cls, data, closed='right', name=None, copy=False):
             Name to be stored in the index.
         copy : boolean, default False
             by-default copy the data, this is compat only and ignored
+        dtype : dtype or None, default None
+            If None, dtype will be inferred
+
+            ..versionadded:: 0.23.0
 
         Examples
         --------
-        >>>  pd.IntervalIndex.from_tuples([(0, 1), (1,2)])
+        >>>  pd.IntervalIndex.from_tuples([(0, 1), (1, 2)])
         IntervalIndex([(0, 1], (1, 2]],
                       closed='right', dtype='interval[int64]')
 
@@ -559,8 +585,6 @@ def from_tuples(cls, data, closed='right', name=None, copy=False):
                                     right array
         IntervalIndex.from_breaks : Construct an IntervalIndex from an array of
                                     splits
-        IntervalIndex.from_intervals : Construct an IntervalIndex from an array
-                                       of Interval objects
         """
         if len(data):
             left, right = [], []
@@ -571,15 +595,22 @@ def from_tuples(cls, data, closed='right', name=None, copy=False):
             if isna(d):
                 lhs = rhs = np.nan
             else:
-                lhs, rhs = d
+                try:
+                    # need list of length 2 tuples, e.g. [(0, 1), (1, 2), ...]
+                    lhs, rhs = d
+                except ValueError:
+                    msg = ('IntervalIndex.from_tuples requires tuples of '
+                           'length 2, got {tpl}').format(tpl=d)
+                    raise ValueError(msg)
+                except TypeError:
+                    msg = ('IntervalIndex.from_tuples received an invalid '
+                           'item, {tpl}').format(tpl=d)
+                    raise TypeError(msg)
             left.append(lhs)
             right.append(rhs)
 
-        # TODO
-        # if we have nulls and we previous had *only*
-        # integer data, then we have changed the dtype
-
-        return cls.from_arrays(left, right, closed, name=name, copy=False)
+        return cls.from_arrays(left, right, closed, name=name, copy=False,
+                               dtype=dtype)
 
     def to_tuples(self, na_tuple=True):
         """
@@ -921,7 +952,7 @@ def get_loc(self, key, method=None):
         Examples
         ---------
         >>> i1, i2 = pd.Interval(0, 1), pd.Interval(1, 2)
-        >>> index = pd.IntervalIndex.from_intervals([i1, i2])
+        >>> index = pd.IntervalIndex([i1, i2])
         >>> index.get_loc(1)
         0
 
@@ -937,7 +968,7 @@ def get_loc(self, key, method=None):
         relevant intervals.
 
         >>> i3 = pd.Interval(0, 2)
-        >>> overlapping_index = pd.IntervalIndex.from_intervals([i2, i3])
+        >>> overlapping_index = pd.IntervalIndex([i2, i3])
         >>> overlapping_index.get_loc(1.5)
         array([0, 1], dtype=int64)
         """

pandas/core/reshape/tile.py

@@ -348,8 +348,7 @@ def _format_labels(bins, precision, right=True,
         # account that we are all right closed
         v = adjust(labels[0].left)
 
-        i = IntervalIndex.from_intervals(
-            [Interval(v, labels[0].right, closed='right')])
+        i = IntervalIndex([Interval(v, labels[0].right, closed='right')])
         labels = i.append(labels[1:])
 
     return labels

pandas/tests/categorical/test_constructors.py

@@ -76,9 +76,7 @@ def test_constructor_unsortable(self):
     def test_constructor_interval(self):
         result = Categorical([Interval(1, 2), Interval(2, 3), Interval(3, 6)],
                              ordered=True)
-        ii = IntervalIndex.from_intervals([Interval(1, 2),
-                                           Interval(2, 3),
-                                           Interval(3, 6)])
+        ii = IntervalIndex([Interval(1, 2), Interval(2, 3), Interval(3, 6)])
         exp = Categorical(ii, ordered=True)
         tm.assert_categorical_equal(result, exp)
         tm.assert_index_equal(result.categories, ii)