Repository: stanfordnlp/dspy

Issue:
Add ability to return a predictor instead of modifying in place.
Currently, to load a predictor after optimization, you need to do it in two lines:
```python
predictor = dspy.Predict("question -> answer")
predictor.load(saved_path)
```

Desired behavior
```python
predictor = dspy.Predict("question -> answer").load(saved_path, return_self=True)
```

This fix is as adding a bool to the `load` method of `BaseModule` to return self.


Discussion:

Patch:
diff --git a/dspy/predict/predict.py b/dspy/predict/predict.py
index 7188044ed7..0f93fd2781 100644
--- a/dspy/predict/predict.py
+++ b/dspy/predict/predict.py
@@ -10,15 +10,12 @@
 from dspy.primitives.program import Module
 from dspy.signatures.signature import ensure_signature, signature_to_template
 from dspy.utils.callback import with_callbacks
-
-
 from dspy.adapters.image_utils import Image
 
 @lru_cache(maxsize=None)
 def warn_once(msg: str):
     logging.warning(msg)
 
-
 class Predict(Module, Parameter):
     def __init__(self, signature, _parse_values=True, callbacks=None, **config):
         self.stage = random.randbytes(8).hex()
@@ -71,10 +68,13 @@ def load_state(self, state, use_legacy_loading=False):
             state (dict): The saved state of a `Predict` object.
             use_legacy_loading (bool): Whether to use the legacy loading method. Only use it when you are loading a
                 saved state from a version of DSPy prior to v2.5.3.
+        Returns:
+            self: Returns self to allow method chaining
         """
         if use_legacy_loading:
             self._load_state_legacy(state)
-            return
+            return self
+            
         if "signature" not in state:
             # Check if the state is from a version of DSPy prior to v2.5.3.
             raise ValueError(
@@ -102,10 +102,14 @@ def load_state(self, state, use_legacy_loading=False):
         if "extended_signature" in state:
             self.extended_signature = self.extended_signature.load_state(state["extended_signature"])
 
+        return self
+
     def _load_state_legacy(self, state):
         """Legacy state loading for backwards compatibility.
 
         This method is used to load the saved state of a `Predict` object from a version of DSPy prior to v2.5.3.
+        Returns:
+            self: Returns self to allow method chaining
         """
         for name, value in state.items():
             setattr(self, name, value)
@@ -130,6 +134,21 @@ def _load_state_legacy(self, state):
             *_, last_key = self.extended_signature.fields.keys()
             self.extended_signature = self.extended_signature.with_updated_fields(last_key, prefix=prefix)
 
+        return self
+
+    def load(self, path, return_self=False):
+        """Load a saved state from a file.
+        
+        Args:
+            path (str): Path to the saved state file
+            return_self (bool): If True, returns self to allow method chaining. Default is False for backwards compatibility.
+        
+        Returns:
+            Union[None, Predict]: Returns None if return_self is False (default), returns self if return_self is True
+        """
+        super().load(path)
+        return self if return_self else None
+
     @with_callbacks
     def __call__(self, **kwargs):
         return self.forward(**kwargs)
@@ -213,8 +232,6 @@ def old_generate(demos, signature, kwargs, config, lm, stage):
         with dsp.settings.context(lm=lm, query_only=True):
             x, C = dsp.generate(template, **config)(x, stage=stage)
 
-    # assert stage in x, "The generated (input, output) example was not stored"
-
     completions = []
 
     for c in C:
@@ -279,7 +296,6 @@ def v2_5_generate(lm, lm_kwargs, signature, demos, inputs, _parse_values=True):
         lm, lm_kwargs=lm_kwargs, signature=signature, demos=demos, inputs=inputs, _parse_values=_parse_values
     )
 
-
 # TODO: get some defaults during init from the context window?
 # # TODO: FIXME: Hmm, I guess expected behavior is that contexts can
 # affect execution. Well, we need to determine whether context dominates, __init__ demoninates, or forward dominates.


Test patch:
diff --git a/tests/predict/test_predict.py b/tests/predict/test_predict.py
index 8d0121eedd..3fb4fce4e1 100644
--- a/tests/predict/test_predict.py
+++ b/tests/predict/test_predict.py
@@ -218,3 +218,48 @@ class OutputOnlySignature(dspy.Signature):
     lm = DummyLM([{"output": "short answer"}])
     dspy.settings.configure(lm=lm)
     assert predictor().output == "short answer"
+
+
+
+def test_chainable_load(tmp_path):
+    """Test both traditional and chainable load methods."""
+    
+    file_path = tmp_path / "test_chainable.json"
+    
+    
+    original = Predict("question -> answer")
+    original.demos = [{"question": "test", "answer": "response"}]
+    original.save(file_path)
+    
+    
+    traditional = Predict("question -> answer")
+    traditional.load(file_path)
+    assert traditional.demos == original.demos
+    
+    
+    chainable = Predict("question -> answer").load(file_path, return_self=True)
+    assert chainable is not None  
+    assert chainable.demos == original.demos
+    
+    
+    assert chainable.signature.dump_state() == original.signature.dump_state()
+    
+    
+    result = Predict("question -> answer").load(file_path)
+    assert result is None
+
+def test_load_state_chaining():
+    """Test that load_state returns self for chaining."""
+    original = Predict("question -> answer")
+    original.demos = [{"question": "test", "answer": "response"}]
+    state = original.dump_state()
+    
+    
+    new_instance = Predict("question -> answer").load_state(state)
+    assert new_instance is not None
+    assert new_instance.demos == original.demos
+    
+    
+    legacy_instance = Predict("question -> answer").load_state(state, use_legacy_loading=True)
+    assert legacy_instance is not None
+    assert legacy_instance.demos == original.demos
\ No newline at end of file