From b5fe3f79d755c722960412bac7a426e9f40aa751 Mon Sep 17 00:00:00 2001
From: yichen8 <43142019+yichen8@users.noreply.github.com>
Date: Thu, 14 Feb 2019 21:17:05 +0800
Subject: [PATCH 1/2] fix the function `find_common_types` bug

` types[0]` can raise a KeyError when `types` is a `pd.Series` . see issue #25270
---
 pandas/core/dtypes/cast.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pandas/core/dtypes/cast.py b/pandas/core/dtypes/cast.py
index f6561948df99a..2f957d1cab6cb 100644
--- a/pandas/core/dtypes/cast.py
+++ b/pandas/core/dtypes/cast.py
@@ -1075,7 +1075,7 @@ def find_common_type(types):
 
     Parameters
     ----------
-    types : list of dtypes
+    types :  list_like
 
     Returns
     -------
@@ -1090,7 +1090,7 @@ def find_common_type(types):
     if len(types) == 0:
         raise ValueError('no types given')
 
-    first = types[0]
+    first = types[:1]
 
     # workaround for find_common_type([np.dtype('datetime64[ns]')] * 2)
     # => object

From ccca752414a457e2d41f9d0c5569cacfa8feeff1 Mon Sep 17 00:00:00 2001
From: yichen8 <43142019+yichen8@users.noreply.github.com>
Date: Sun, 17 Feb 2019 10:56:47 +0800
Subject: [PATCH 2/2] update find_common_type() statement about first.

Last modification can't pass test, so fix it and now it can pass test.
---
 pandas/core/dtypes/cast.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/core/dtypes/cast.py b/pandas/core/dtypes/cast.py
index 2f957d1cab6cb..6c4a801155899 100644
--- a/pandas/core/dtypes/cast.py
+++ b/pandas/core/dtypes/cast.py
@@ -1090,7 +1090,7 @@ def find_common_type(types):
     if len(types) == 0:
         raise ValueError('no types given')
 
-    first = types[:1]
+    first = [t for t in types][0]
 
     # workaround for find_common_type([np.dtype('datetime64[ns]')] * 2)
     # => object