[API change] Getting rid of the create method for observers v0.99999

docs/observers.rst

@@ -583,7 +583,11 @@ To add a SqlObserver from python code do:
 
     from sacred.observers import SqlObserver
 
-    ex.observers.append(SqlObserver.create('sqlite:///foo.db'))
+    ex.observers.append(SqlObserver('sqlite:///foo.db'))
+
+    # It's also possible to instantiate a SqlObserver with an existing
+    # engine and session with:
+    ex.observers.append(SqlObserver.create_from(my_engine, my_session))
 
 
 Schema

sacred/observers/sql.py

@@ -3,6 +3,7 @@
 
 import json
 from threading import Lock
+import warnings
 
 from sacred.commandline_options import CommandLineOption
 from sacred.observers.base import RunObserver
@@ -17,21 +18,37 @@
 class SqlObserver(RunObserver):
     @classmethod
     def create(cls, url, echo=False, priority=DEFAULT_SQL_PRIORITY):
+        warnings.warn(
+            "SqlObserver.create(...) is deprecated. Please use"
+            " SqlObserver(...) instead.",
+            DeprecationWarning,
+        )
+        return cls(url, echo, priority)
+
+    def __init__(self, url, echo=False, priority=DEFAULT_SQL_PRIORITY):
         from sqlalchemy.orm import sessionmaker, scoped_session
         import sqlalchemy as sa
 
         engine = sa.create_engine(url, echo=echo)
         session_factory = sessionmaker(bind=engine)
         # make session thread-local to avoid problems with sqlite (see #275)
         session = scoped_session(session_factory)
-        return cls(engine, session, priority)
+        self.engine = engine
+        self.session = session
+        self.priority = priority
+        self.run = None
+        self.lock = Lock()
 
-    def __init__(self, engine, session, priority=DEFAULT_SQL_PRIORITY):
+    @classmethod
+    def create_from(cls, engine, session, priority=DEFAULT_SQL_PRIORITY):
+        """Instantiate a SqlObserver with an existing engine and session"""
+        self = cls.__new__(cls)  # skip __init__ call
         self.engine = engine
         self.session = session
         self.priority = priority
         self.run = None
         self.lock = Lock()
+        return self
 
     def started_event(
         self, ex_info, command, host_info, start_time, config, meta_info, _id

tests/test_observers/test_sql_observer.py

@@ -48,7 +48,7 @@ def session(engine):
 
 @pytest.fixture
 def sql_obs(session, engine):
-    return SqlObserver(engine, session)
+    return SqlObserver.create_from(engine, session)
 
 
 @pytest.fixture
@@ -228,7 +228,7 @@ def test_fs_observer_resource_event(sql_obs, sample_run, session, tmpfile):
 
 
 def test_fs_observer_doesnt_duplicate_sources(sql_obs, sample_run, session, tmpfile):
-    sql_obs2 = SqlObserver(sql_obs.engine, session)
+    sql_obs2 = SqlObserver.create_from(sql_obs.engine, session)
     sample_run["_id"] = None
     sample_run["ex_info"]["sources"] = [[tmpfile.name, tmpfile.md5sum]]
 
@@ -240,7 +240,7 @@ def test_fs_observer_doesnt_duplicate_sources(sql_obs, sample_run, session, tmpf
 
 
 def test_fs_observer_doesnt_duplicate_resources(sql_obs, sample_run, session, tmpfile):
-    sql_obs2 = SqlObserver(sql_obs.engine, session)
+    sql_obs2 = SqlObserver.create_from(sql_obs.engine, session)
     sample_run["_id"] = None
     sample_run["ex_info"]["sources"] = [[tmpfile.name, tmpfile.md5sum]]
 
@@ -255,7 +255,7 @@ def test_fs_observer_doesnt_duplicate_resources(sql_obs, sample_run, session, tm
 
 
 def test_sql_observer_equality(sql_obs, engine, session):
-    sql_obs2 = SqlObserver(engine, session)
+    sql_obs2 = SqlObserver.create_from(engine, session)
     assert sql_obs == sql_obs2
 
     assert not sql_obs != sql_obs2

tests/test_observers/test_sql_observer_not_installed.py

@@ -12,7 +12,7 @@ def ex():
 @pytest.mark.skipif(has_sqlalchemy, reason="We are testing the import error.")
 def test_importerror_sql(ex):
     with pytest.raises(ImportError):
-        ex.observers.append(SqlObserver.create("some_uri"))
+        ex.observers.append(SqlObserver("some_uri"))
 
         @ex.config
         def cfg():