BUG: Fix json_normalize throws TypeError with array of values and ecord_prefix (pandas-dev#21536)

Author: vuminhle

pandas/io/json/normalize.py

@@ -259,7 +259,8 @@ def _recursive_extract(data, path, seen_meta, level=0):
     result = DataFrame(records)
 
     if record_prefix is not None:
-        result.rename(columns=lambda x: record_prefix + x, inplace=True)
+        result.rename(columns=lambda x: "{p}{c}".format(
+            p=record_prefix, c=x), inplace=True)
 
     # Data types, a problem
     for k, v in compat.iteritems(meta_vals):

pandas/tests/io/json/test_normalize.py

@@ -123,6 +123,12 @@ def test_simple_normalize_with_separator(self, deep_nested):
                           'country', 'states_name']).sort_values()
         assert result.columns.sort_values().equals(expected)
 
+    def test_value_array_record_prefix(self):
+        #GH 21536
+        result = json_normalize({'A': [1, 2]}, 'A', record_prefix='Prefix.')
+        expected = DataFrame([[1], [2]], columns=['Prefix.0'])
+        tm.assert_frame_equal(result.reindex_like(expected), expected)
+
     def test_more_deeply_nested(self, deep_nested):
 
         result = json_normalize(deep_nested, ['states', 'cities'],