add objects get method (piccolo-orm#183)

* add simple get method

* update docs

* minor tweak to docs - mention ``None`` is returned if ``get`` finds no match

Co-authored-by: Daniel Townsend <[email protected]>

Author: aminalaee

docs/src/piccolo/query_types/objects.rst

@@ -28,6 +28,13 @@ To get certain rows:
     >>> Band.objects().where(Band.name == 'Pythonistas').run_sync()
     [<Band: 1>]
 
+To get a single row (or ``None`` if it doesn't exist):
+
+.. code-block:: python
+
+    >>> Band.objects().get(Band.name == 'Pythonistas').run_sync()
+    <Band: 1>
+
 To get the first row:
 
 .. code-block:: python

piccolo/query/methods/objects.py

@@ -30,7 +30,7 @@ class GetOrCreate:
     defaults: t.Dict[t.Union[Column, str], t.Any]
 
     async def run(self):
-        instance = await self.query.where(self.where).first().run()
+        instance = await self.query.get(self.where).run()
         if instance:
             return instance
 
@@ -99,6 +99,11 @@ def first(self) -> Objects:
         self.limit_delegate.first()
         return self
 
+    def get(self, where: Combinable) -> Objects:
+        self.where_delegate.where(where)
+        self.limit_delegate.first()
+        return self
+
     def offset(self, number: int) -> Objects:
         self.offset_delegate.offset(number)
         return self

tests/table/test_objects.py

@@ -60,6 +60,13 @@ def test_offset_sqlite(self):
             [i.name for i in response], ["Pythonistas", "Rustaceans"]
         )
 
+    def test_get(self):
+        self.insert_row()
+
+        band = Band.objects().get(Band.name == "Pythonistas").run_sync()
+
+        self.assertTrue(band.name == "Pythonistas")
+
     def test_get_or_create(self):
         Band.objects().get_or_create(
             Band.name == "Pink Floyd", defaults={"popularity": 100}