BigQuery: added methods for getting keys, items and dict (#4393)

* added methods for getting keys, items and dict

This change enables to retrieve the row as a dict and iterate the keys and/or items, like with a normal dict; in other words, making the Row object a dict-like object:

>>> row.dict()
{'name': 'Isabel', 'profession': 'bridge builder'}
>>> for k, v in row.items():
>>> for k in row.keys():

* fixed row length

* removed whitespace from blank lines

* removed trailing whitespace

* responding to failed cover check

* added docstrings

* update unit tests

* Update test_table.py

* .keys() and .items() into generators

* get method for Row

* get method for Row

* get method for Row

* Update table.py

* Update test_table.py

* Update test_table.py

bigquery/google/cloud/bigquery/table.py

@@ -785,6 +785,47 @@ def __init__(self, values, field_to_index):
     def values(self):
         return self._xxx_values
 
+    def keys(self):
+        """
+        Return keys as of a dict:
+        >>> Row(('a', 'b'), {'x': 0, 'y': 1}).keys()
+        ['x', 'y']
+        """
+        keys = self._xxx_field_to_index.keys()
+        return keys
+
+    def items(self):
+        """
+        Return items as of a dict:
+        >>> Row(('a', 'b'), {'x': 0, 'y': 1}).items()
+        [('x', 'a'), ('y', 'b')]
+        """
+        items = [
+            (k, self._xxx_values[i])
+            for k, i
+            in self._xxx_field_to_index.items()
+        ]
+        return items
+
+    def get(self, key, default=None):
+        """
+        Return value under specified key
+        Defaults to None or specified default
+        if key does not exist:
+        >>> Row(('a', 'b'), {'x': 0, 'y': 1}).get('x')
+        'a'
+        >>> Row(('a', 'b'), {'x': 0, 'y': 1}).get('z')
+        None
+        >>> Row(('a', 'b'), {'x': 0, 'y': 1}).get('z', '')
+        ''
+        >>> Row(('a', 'b'), {'x': 0, 'y': 1}).get('z', default = '')
+        ''
+        """
+        index = self._xxx_field_to_index.get(key)
+        if index is None:
+            return default
+        return self._xxx_values[index]
+
     def __getattr__(self, name):
         value = self._xxx_field_to_index.get(name)
         if value is None:

bigquery/tests/unit/test_table.py

@@ -765,6 +765,13 @@ def test_row(self):
         self.assertEqual(row['c'], 3)
         self.assertEqual(len(row), 3)
         self.assertEqual(row.values(), VALUES)
+        self.assertEqual(set(row.keys()), set({'a': 1, 'b': 2, 'c': 3}.keys()))
+        self.assertEqual(set(row.items()),
+                         set({'a': 1, 'b': 2, 'c': 3}.items()))
+        self.assertEqual(row.get('a'), 1)
+        self.assertEqual(row.get('d'), None)
+        self.assertEqual(row.get('d', ''), '')
+        self.assertEqual(row.get('d', default=''), '')
         self.assertEqual(repr(row),
                          "Row((1, 2, 3), {'a': 0, 'b': 1, 'c': 2})")
         self.assertFalse(row != row)