feat: Implement Slider class for JupyterViz

This provides API parity with the previous Tornado viz.

mesa/experimental/UserParam.py

@@ -0,0 +1,56 @@
+class UserParam:
+    _ERROR_MESSAGE = "Missing or malformed inputs for '{}' Option '{}'"
+
+    def maybe_raise_error(self, param_type, valid):
+        if valid:
+            return
+        msg = self._ERROR_MESSAGE.format(param_type, self.label)
+        raise ValueError(msg)
+
+
+class Slider(UserParam):
+    """
+    A number-based slider input with settable increment.
+
+    Example:
+
+    slider_option = Slider("My Slider", value=123, min=10, max=200, step=0.1)
+
+    Args:
+        label: The displayed label in the UI
+        value: The initial value of the slider
+        min: The minimum possible value of the slider
+        max: The maximum possible value of the slider
+        step: The step between min and max for a range of possible values
+        dtype: either int or float
+    """
+
+    def __init__(
+        self,
+        label="",
+        value=None,
+        min=None,
+        max=None,
+        step=1,
+        dtype=None,
+    ):
+        self.label = label
+        self.value = value
+        self.min = min
+        self.max = max
+        self.step = step
+
+        # Validate option type to make sure values are supplied properly
+        valid = not (self.value is None or self.min is None or self.max is None)
+        self.maybe_raise_error("slider", valid)
+
+        if dtype is None:
+            self.is_float_slider = self._check_values_are_float(value, min, max, step)
+        else:
+            self.is_float_slider = dtype == float
+
+    def _check_values_are_float(self, value, min, max, step):
+        return any(isinstance(n, float) for n in (value, min, max, step))
+
+    def get(self, attr):
+        return getattr(self, attr)

mesa/experimental/__init__.py

@@ -1 +1 @@
-from .jupyter_viz import JupyterViz, make_text  # noqa
+from .jupyter_viz import JupyterViz, make_text, Slider  # noqa

mesa/experimental/jupyter_viz.py

@@ -7,6 +7,7 @@
 from solara.alias import rv
 
 import mesa.experimental.components.matplotlib as components_matplotlib
+from mesa.experimental.UserParam import Slider
 
 # Avoid interactive backend
 plt.switch_backend("agg")
@@ -43,7 +44,7 @@ def JupyterViz(
     # 1. Set up model parameters
     user_params, fixed_params = split_model_params(model_params)
     model_parameters, set_model_parameters = solara.use_state(
-        {**fixed_params, **{k: v["value"] for k, v in user_params.items()}}
+        {**fixed_params, **{k: v.get("value") for k, v in user_params.items()}}
     )
 
     # 2. Set up Model
@@ -254,6 +255,8 @@ def split_model_params(model_params):
 
 
 def check_param_is_fixed(param):
+    if isinstance(param, Slider):
+        return False
     if not isinstance(param, dict):
         return True
     if "type" not in param:
@@ -273,13 +276,26 @@ def UserInputs(user_params, on_change=None):
     """
 
     for name, options in user_params.items():
-        # label for the input is "label" from options or name
-        label = options.get("label", name)
-        input_type = options.get("type")
 
         def change_handler(value, name=name):
             on_change(name, value)
 
+        if isinstance(options, Slider):
+            slider_class = (
+                solara.SliderFloat if options.is_float_slider else solara.SliderInt
+            )
+            slider_class(
+                options.label,
+                on_value=change_handler,
+                min=options.min,
+                max=options.max,
+                step=options.step,
+            )
+            continue
+
+        # label for the input is "label" from options or name
+        label = options.get("label", name)
+        input_type = options.get("type")
         if input_type == "SliderInt":
             solara.SliderInt(
                 label,

tests/test_jupyter_viz.py

@@ -4,7 +4,7 @@
 import ipyvuetify as vw
 import solara
 
-from mesa.experimental.jupyter_viz import JupyterViz, UserInputs
+from mesa.experimental.jupyter_viz import JupyterViz, Slider, UserInputs
 
 
 class TestMakeUserInput(unittest.TestCase):
@@ -133,3 +133,17 @@ def test_call_space_drawer(self, mock_space_matplotlib):
         altspace_drawer.assert_called_with(
             mock_model_class.return_value, agent_portrayal
         )
+
+
+def test_slider():
+    slider_float = Slider("Agent density", 0.8, 0.1, 1.0, 0.1)
+    assert slider_float.is_float_slider
+    assert slider_float.value == 0.8
+    assert slider_float.get("value") == 0.8
+    assert slider_float.min == 0.1
+    assert slider_float.max == 1.0
+    assert slider_float.step == 0.1
+    slider_int = Slider("Homophily", 3, 0, 8, 1)
+    assert not slider_int.is_float_slider
+    slider_dtype_float = Slider("Homophily", 3, 0, 8, 1, dtype=float)
+    assert slider_dtype_float.is_float_slider