From ae39f29061a5174ce962a4af395db93d9fd4cc6a Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Tue, 13 Mar 2018 00:35:47 -0700
Subject: [PATCH 1/2] Fixed bug with str.split, expand and no pater

---
 pandas/core/strings.py       | 3 ++-
 pandas/tests/test_strings.py | 7 +++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/pandas/core/strings.py b/pandas/core/strings.py
index 11081535cf63f..924550b133c3c 100644
--- a/pandas/core/strings.py
+++ b/pandas/core/strings.py
@@ -1615,7 +1615,8 @@ def cons_row(x):
             if result:
                 # propagate nan values to match longest sequence (GH 18450)
                 max_len = max(len(x) for x in result)
-                result = [x * max_len if x[0] is np.nan else x for x in result]
+                result = [x * max_len if len(x) and x[0] is np.nan else x for x
+                          in result]
 
         if not isinstance(expand, bool):
             raise ValueError("expand must be True or False")
diff --git a/pandas/tests/test_strings.py b/pandas/tests/test_strings.py
index a878d6ed7b052..8ab1ee5574aab 100644
--- a/pandas/tests/test_strings.py
+++ b/pandas/tests/test_strings.py
@@ -2144,6 +2144,13 @@ def test_split_nan_expand(self):
         # tm.assert_frame_equal does not differentiate
         assert all(np.isnan(x) for x in result.iloc[1])
 
+    def test_split_no_pat_and_expand(self):
+        # GH 20002
+        df = DataFrame({'foo': ['']})
+        exp = DataFrame([[]])
+        res = df['foo'].str.split(expand=True)
+        tm.assert_frame_equal(res, exp)
+
     def test_split_with_name(self):
         # GH 12617
 

From 980f13647ceb94b93f688a870789c2f0eb05b02a Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Tue, 13 Mar 2018 00:36:12 -0700
Subject: [PATCH 2/2] Updated whatsnew

---
 doc/source/whatsnew/v0.23.0.txt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/doc/source/whatsnew/v0.23.0.txt b/doc/source/whatsnew/v0.23.0.txt
index f686a042c1a74..45dd61e4e7571 100644
--- a/doc/source/whatsnew/v0.23.0.txt
+++ b/doc/source/whatsnew/v0.23.0.txt
@@ -936,6 +936,7 @@ Indexing
 - Bug in :class:`IntervalIndex` where set operations that returned an empty ``IntervalIndex`` had the wrong dtype (:issue:`19101`)
 - Bug in :meth:`DataFrame.drop_duplicates` where no ``KeyError`` is raised when passing in columns that don't exist on the ``DataFrame`` (issue:`19726`)
 - Bug in ``Index`` subclasses constructors that ignore unexpected keyword arguments (:issue:`19348`)
+- Bug in :meth:`Series.str.split` where splitting an empty string without a `pater` and with ``expand=True`` would raise an ``IndexError`` (:issue:`20002`)
 
 
 MultiIndex