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_concat_rangeindex_... now returns an empty RangeIndex for empty ranges #18214

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Merged
merged 4 commits into from
Nov 11, 2017
Merged

_concat_rangeindex_... now returns an empty RangeIndex for empty ranges #18214

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7df9398
`_concat_rangeindex_same_dtype` now returns an empty `Int64Index` for…
Nov 10, 2017
7d4c7c7
Replaced the empty integer index with and empty range index
Nov 10, 2017
0f5f41e
Fixed pep issues
Nov 10, 2017
3210504
Removed `else` before the return statement
Nov 11, 2017
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17 changes: 6 additions & 11 deletions pandas/core/dtypes/concat.py
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Original file line number Diff line number Diff line change
Expand Up @@ -571,6 +571,7 @@ def _concat_rangeindex_same_dtype(indexes):
indexes = [RangeIndex(3), RangeIndex(3, 6)] -> RangeIndex(6)
indexes = [RangeIndex(3), RangeIndex(4, 6)] -> Int64Index([0,1,2,4,5])
"""
from pandas import Int64Index, RangeIndex

start = step = next = None

Expand All @@ -587,14 +588,12 @@ def _concat_rangeindex_same_dtype(indexes):
elif step is None:
# First non-empty index had only one element
if obj._start == start:
from pandas import Int64Index
return _concat_index_same_dtype(indexes, klass=Int64Index)
step = obj._start - start

non_consecutive = ((step != obj._step and len(obj) > 1) or
(next is not None and obj._start != next))
if non_consecutive:
from pandas import Int64Index
return _concat_index_same_dtype(indexes, klass=Int64Index)

if step is not None:
Expand All @@ -604,12 +603,8 @@ def _concat_rangeindex_same_dtype(indexes):
# Get the stop value from "next" or alternatively
# from the last non-empty index
stop = non_empty_indexes[-1]._stop if next is None else next
else:
# Here all "indexes" had 0 length, i.e. were empty.
# Simply take start, stop, and step from the last empty index.
obj = indexes[-1]
start = obj._start
step = obj._step
stop = obj._stop

return indexes[0].__class__(start, stop, step)
return RangeIndex(start, stop, step)

# Here all "indexes" had 0 length, i.e. were empty.
# In this case return an empty range index.
return RangeIndex(0, 0)
4 changes: 2 additions & 2 deletions pandas/tests/indexes/test_range.py
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Original file line number Diff line number Diff line change
Expand Up @@ -971,8 +971,8 @@ def test_append(self):
([RI(1, 5, 2), RI(5, 6)], RI(1, 6, 2)),
([RI(1, 3, 2), RI(4, 7, 3)], RI(1, 7, 3)),
([RI(-4, 3, 2), RI(4, 7, 2)], RI(-4, 7, 2)),
([RI(-4, -8), RI(-8, -12)], RI(-8, -12)),
([RI(-4, -8), RI(3, -4)], RI(3, -8)),
([RI(-4, -8), RI(-8, -12)], RI(0, 0)),
([RI(-4, -8), RI(3, -4)], RI(0, 0)),
([RI(-4, -8), RI(3, 5)], RI(3, 5)),
([RI(-4, -2), RI(3, 5)], I64([-4, -3, 3, 4])),
([RI(-2,), RI(3, 5)], RI(3, 5)),
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