Fixes bug while reading json (iterator failed to be created twice) (#26)

_unittests/ut_df/data/example.json

@@ -0,0 +1,2 @@
+{"a": 1, "b": 2}
+{"a": 3, "b": 4}

_unittests/ut_df/data/example2.json

@@ -0,0 +1 @@
+[{"a":1,"b":2},{"a":3,"b":4}]

_unittests/ut_df/test_dataframe_io_helpers.py

@@ -145,6 +145,8 @@ def test_read_json_raw_head(self):
         h1 = it.head()
         h2 = it.head()
         self.assertEqualDataFrame(h1, h2)
+        self.assertGreater(h1.shape[0], 1)
+        self.assertGreater(h2.shape[0], 1)
 
     def test_pandas_json_chunksize(self):
         jsonl = '''{"a": 1, "b": 2}
@@ -186,6 +188,28 @@ def test_read_json_rows2_head(self):
         self.assertNotEmpty(h2)
         self.assertEqualDataFrame(h1, h2)
 
+    def test_read_json_rows_file_head(self):
+        data = self.abs_path_join(__file__, 'data', 'example2.json')
+        dfs = pandas.read_json(data, orient='records')
+        self.assertEqual(dfs.shape, (2, 2))
+        it = StreamingDataFrame.read_json(data)
+        h1 = it.head()
+        h2 = it.head()
+        self.assertNotEmpty(h1)
+        self.assertNotEmpty(h2)
+        self.assertEqualDataFrame(h1, h2)
+
+    def test_read_json_rows_file_lines_head(self):
+        data = self.abs_path_join(__file__, 'data', 'example.json')
+        dfs = pandas.read_json(data, orient='records', lines=True)
+        self.assertEqual(dfs.shape, (2, 2))
+        it = StreamingDataFrame.read_json(data, lines="stream")
+        h1 = it.head()
+        h2 = it.head()
+        self.assertNotEmpty(h1)
+        self.assertNotEmpty(h2)
+        self.assertEqualDataFrame(h1, h2)
+
     def test_read_json_ijson(self):
         it = StreamingDataFrame.read_json(
             BytesIO(TestDataFrameIOHelpers.text_json))

pandas_streaming/df/dataframe.py

@@ -178,7 +178,7 @@ def read_json(*args, chunksize=100000, flatten=False, **kwargs) -> 'StreamingDat
         and it must be defined to return an iterator.
         If *lines* is True, the function falls back into
         :epkg:`pandas:read_json`, otherwise it used
-        @see fn enumerate_json_items. If *lines is ``'stream'``,
+        @see fn enumerate_json_items. If *lines* is ``'stream'``,
         *enumerate_json_items* is called with parameter
         ``lines=True``.
         Parameter *flatten* uses the trick described at
@@ -212,6 +212,13 @@ def read_json(*args, chunksize=100000, flatten=False, **kwargs) -> 'StreamingDat
             it = StreamingDataFrame.read_json(BytesIO(data))
             dfs = list(it)
             print(dfs)
+
+        .. index:: IncompleteJSONError
+
+        The parsed json must have an empty line at the end otherwise
+        the following exception is raised:
+        `ijson.common.IncompleteJSONError: `
+        `parse error: unallowed token at this point in JSON text`.
         """
         if not isinstance(chunksize, int) or chunksize <= 0:
             raise ValueError(  # pragma: no cover
@@ -228,7 +235,8 @@ def read_json(*args, chunksize=100000, flatten=False, **kwargs) -> 'StreamingDat
             del kwargs['lines']
 
             def localf(a0=args[0]):
-                a0.seek(0)
+                if hasattr(a0, 'seek'):
+                    a0.seek(0)
                 return enumerate_json_items(
                     a0, encoding=kwargs.get('encoding', None), lines=True,
                     flatten=flatten)
@@ -280,6 +288,7 @@ def fct2(args=args, chunksize=chunksize, kw=kwargs.copy()):
                 **kwargs_create)
 
         def fct3(st=st, args=args, chunksize=chunksize, kw=kwargs.copy()):
+            st.seek(0)
             for r in pandas.read_json(
                     st, *args, chunksize=chunksize, nrows=chunksize,
                     lines=True, **kw):
@@ -920,8 +929,9 @@ def __getitem__(self, *args):
 
             def iterate_col():
                 "iterate on one column"
+                one_col = [cols]
                 for df in iter_creation():
-                    yield df[[cols]]
+                    yield df[one_col]
             return StreamingSeries(iterate_col, **self.get_kwargs())
 
         if not isinstance(cols, list):

pandas_streaming/df/dataframe_io_helpers.py

@@ -113,11 +113,13 @@ def flatten_dictionary(dico, sep="_"):
     """
     Flattens a dictionary with nested structure to a dictionary with no
     hierarchy.
+
     :param dico: dictionary to flatten
     :param sep: string to separate dictionary keys by
     :return: flattened dictionary
 
-    Inspired from `flatten_json <https://github.com/amirziai/flatten/blob/master/flatten_json.py>`_.
+    Inspired from `flatten_json
+    <https://github.com/amirziai/flatten/blob/master/flatten_json.py>`_.
     """
     flattened_dict = {}
 
@@ -223,6 +225,11 @@ def enumerate_json_items(filename, encoding=None, lines=False, flatten=False, fL
 
             for item in enumerate_json_items(text_json):
                 print(item)
+
+    The parsed json must have an empty line at the end otherwise
+    the following exception is raised:
+    `ijson.common.IncompleteJSONError: `
+    `parse error: unallowed token at this point in JSON text`.
     """
     if isinstance(filename, str):
         if "{" not in filename and os.path.exists(filename):