add whatsnew entry

Author: Jiang Yue

doc/source/whatsnew/v0.25.0.rst

@@ -133,6 +133,7 @@ Other Enhancements
 - :meth:`DataFrame.describe` now formats integer percentiles without decimal point (:issue:`26660`)
 - Added support for reading SPSS .sav files using :func:`read_spss` (:issue:`26537`)
 - Added new option ``plotting.backend`` to be able to select a plotting backend different than the existing ``matplotlib`` one. Use ``pandas.set_option('plotting.backend', '<backend-module>')`` where ``<backend-module`` is a library implementing the pandas plotting API (:issue:`14130`)
+- :meth:`io.json.json_normalize` now accepts a `fill_value` argument to fill NaN fields in given columns (:issue:`16918`)
 
 .. _whatsnew_0250.api_breaking:
 

pandas/_libs/lib.pyx

@@ -321,7 +321,8 @@ def dicts_to_array(dicts: list, columns: list, fill_value=None):
 
     result = np.empty((n, k), dtype='O')
     if fill_value:
-        onan = [fill_value[col] if col in fill_value else np.nan for col in columns]
+        onan = ([fill_value[col] if col in fill_value
+                else np.nan for col in columns])
     else:
         onan = list(np.full(k, np.nan))
 

pandas/io/json/normalize.py

@@ -109,8 +109,6 @@ def json_normalize(data, record_path=None, meta=None,
     ----------
     data : dict or list of dicts
         Unserialized JSON objects
-    fill_value: dict, default None
-        default na values for specified columns
     record_path : string or list of strings, default None
         Path in each object to list of records. If not passed, data will be
         assumed to be an array of records
@@ -135,6 +133,11 @@ def json_normalize(data, record_path=None, meta=None,
 
         .. versionadded:: 0.20.0
 
+    fill_value : dict, default None
+        default na values for specified columns
+
+        .. versionadded:: 0.25.0
+
     Returns
     -------
     frame : DataFrame

pandas/tests/io/json/test_normalize.py

@@ -38,6 +38,7 @@ def deep_nested():
              }
             ]
 
+
 @pytest.fixture
 def deep_nested_missing():
     # deeply nested data with some missing values
@@ -65,6 +66,7 @@ def deep_nested_missing():
              }
             ]
 
+
 @pytest.fixture
 def state_data():
     return [