Fix #18434

MultiIndex.from_tuples/from_arrays/from_product accept iterators in
python 3. Ensures compatibility
between 2 and 3.

Author: Xbar

doc/source/whatsnew/v0.22.0.txt

@@ -137,6 +137,7 @@ Indexing
 - Bug in :func:`Series.truncate` which raises ``TypeError`` with a monotonic ``PeriodIndex`` (:issue:`17717`)
 - Bug in :func:`DataFrame.groupby` where tuples were interpreted as lists of keys rather than as keys (:issue:`17979`, :issue:`18249`)
 - Bug in :func:`MultiIndex.remove_unused_levels`` which would fill nan values (:issue:`18417`)
+- Bug in :func:`MultiIndex.from_tuples`` which would fail to take zipped tuples in python3 (:issue:`18434`)
 -
 
 I/O

pandas/core/indexes/multi.py

@@ -1162,6 +1162,11 @@ def from_arrays(cls, arrays, sortorder=None, names=None):
         MultiIndex.from_product : Make a MultiIndex from cartesian product
                                   of iterables
         """
+        if not is_list_like(arrays):
+            raise TypeError("Inappropriate input for list of arrays.")
+        elif is_iterator(arrays):
+            arrays = list(arrays)
+
         # Check if lengths of all arrays are equal or not,
         # raise ValueError, if not
         for i in range(1, len(arrays)):
@@ -1206,6 +1211,11 @@ def from_tuples(cls, tuples, sortorder=None, names=None):
         MultiIndex.from_product : Make a MultiIndex from cartesian product
                                   of iterables
         """
+        if not is_list_like(tuples):
+            raise TypeError('Inappropriate input for tuples.')
+        elif is_iterator(tuples):
+            tuples = list(tuples)
+
         if len(tuples) == 0:
             if names is None:
                 msg = 'Cannot infer number of levels from empty list'
@@ -1260,6 +1270,11 @@ def from_product(cls, iterables, sortorder=None, names=None):
         from pandas.core.categorical import _factorize_from_iterables
         from pandas.core.reshape.util import cartesian_product
 
+        if not is_list_like(iterables):
+            raise TypeError("Inappropriate input for iterables.")
+        elif is_iterator(iterables):
+            iterables = list(iterables)
+
         labels, levels = _factorize_from_iterables(iterables)
         labels = cartesian_product(labels)
         return MultiIndex(levels, labels, sortorder=sortorder, names=names)

pandas/tests/indexes/test_multi.py

@@ -674,6 +674,8 @@ def test_from_arrays(self):
 
         result = MultiIndex.from_arrays(arrays)
         assert list(result) == list(self.index)
+        result2 = MultiIndex.from_arrays(iter(arrays))  # iterator as input
+        assert list(result2) == list(self.index)
 
         # infer correctly
         result = MultiIndex.from_arrays([[pd.NaT, Timestamp('20130101')],
@@ -827,6 +829,11 @@ def test_from_product(self):
         tm.assert_index_equal(result, expected)
         assert result.names == names
 
+        # iterator as input
+        result2 = MultiIndex.from_product(iter([first, second]), names=names)
+        assert result2.equals(expected)
+        assert result2.names == names
+
     def test_from_product_empty(self):
         # 0 levels
         with tm.assert_raises_regex(
@@ -1725,8 +1732,15 @@ def test_from_tuples(self):
                                'from empty list',
                                MultiIndex.from_tuples, [])
 
-        idx = MultiIndex.from_tuples(((1, 2), (3, 4)), names=['a', 'b'])
-        assert len(idx) == 2
+        expected = MultiIndex(levels=[[1, 3], [2, 4]],
+                              labels=[[0, 1], [0, 1]],
+                              names=['a', 'b'])
+        res1 = MultiIndex.from_tuples(((1, 2), (3, 4)), names=['a', 'b'])
+        assert expected.names == res1.names
+        assert res1.equals(expected)
+        res2 = MultiIndex.from_tuples(zip([1, 3], [2, 4]), names=['a', 'b'])
+        assert expected.names == res2.names
+        assert res2.equals(expected)
 
     def test_from_tuples_empty(self):
         # GH 16777