Allow interact to use basic type hint annotations (#3908)

* Add basic implementation of type-hint-based `interact`

* Add tests for type annotated interact.

* Update interact documentation to discuss type annotations.

* Use EnumMeta instead of EnumType for backwards compatibility.

docs/source/examples/Using Interact.ipynb

@@ -18,7 +18,9 @@
    "cell_type": "code",
    "execution_count": null,
    "metadata": {
-    "tags": ["remove-cell"]
+    "tags": [
+     "remove-cell"
+    ]
    },
    "outputs": [],
    "source": [
@@ -353,6 +355,111 @@
     "interact(f, x=widgets.Combobox(options=[\"Chicago\", \"New York\", \"Washington\"], value=\"Chicago\"));"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Type Annotations"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "If the function that you are using with interact uses type annotations, `interact` may be able to use those to determine what UI components to use in the auto-generated UI.  For example, given a function with an argument annotated with type `float`"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "def f(x: float):\n",
+    "    return x"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "then `interact` will create a UI with a `FloatText` component without needing to be passed any values or abbreviations."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "interact(f);"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "The following table gives an overview of different annotation types, and how they map to interactive controls:\n",
+    "\n",
+    "<table class=\"table table-condensed table-bordered\">\n",
+    "  <tr><td><strong>Type Annotation</strong></td><td><strong>Widget</strong></td></tr>  \n",
+    "  <tr><td>`bool`</td><td>Checkbox</td></tr>  \n",
+    "  <tr><td>`str`</td><td>Text</td></tr>\n",
+    "  <tr><td>`int`</td><td>IntText</td></tr>\n",
+    "  <tr><td>`float`</td><td>FloatText</td></tr>\n",
+    "  <tr><td>`Enum` subclasses</td><td>Dropdown</td></tr>\n",
+    "</table>\n",
+    "\n",
+    "Other type annotations are ignored."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "If values or abbreviations are passed to the `interact` function, those will override any type annotations when determining what widgets to create."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Parameters which are annotationed with an `Enum` subclass will have a dropdown created whose labels are the names of the enumeration and which pass the corresponding values to the function parameter."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from enum import Enum\n",
+    "\n",
+    "class Color(Enum):\n",
+    "    red = 0\n",
+    "    green = 1\n",
+    "    blue = 2\n",
+    "\n",
+    "def h(color: Color):\n",
+    "    return color"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "When `interact` is used with the function `h`, the Dropdown widget it creates will have options `\"red\"`, `\"green\"` and `\"blue\"` and the values passed to the function will be, correspondingly, `Color.red`, `Color.green` and `Color.blue`."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "interact(h);"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},
@@ -715,7 +822,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 1,
+   "execution_count": null,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -762,9 +869,9 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.10.5"
+   "version": "3.12.2"
   }
  },
  "nbformat": 4,
- "nbformat_minor": 2
+ "nbformat_minor": 4
 }

python/ipywidgets/ipywidgets/widgets/interaction.py

@@ -4,15 +4,16 @@
 """Interact with functions using widgets."""
 
 from collections.abc import Iterable, Mapping
+from enum import EnumMeta as EnumType
 from inspect import signature, Parameter
 from inspect import getcallargs
 from inspect import getfullargspec as check_argspec
 import sys
 
 from IPython import get_ipython
 from . import (Widget, ValueWidget, Text,
-    FloatSlider, IntSlider, Checkbox, Dropdown,
-    VBox, Button, DOMWidget, Output)
+    FloatSlider, FloatText, IntSlider, IntText, Checkbox,
+    Dropdown, VBox, Button, DOMWidget, Output)
 from IPython.display import display, clear_output
 from traitlets import HasTraits, Any, Unicode, observe
 from numbers import Real, Integral
@@ -125,6 +126,8 @@ def _yield_abbreviations_for_parameter(param, kwargs):
             value = kwargs.pop(name)
         elif default is not empty:
             value = default
+        elif param.annotation:
+            value = param.annotation
         else:
             yield not_found
         yield (name, value, default)
@@ -304,6 +307,12 @@ def widget_from_abbrev(cls, abbrev, default=empty):
                     # ignore failure to set default
                     pass
             return widget
+
+        # Try type annotation
+        if isinstance(abbrev, type):
+            widget = cls.widget_from_annotation(abbrev)
+            if widget is not None:
+                return widget
 
         # Try single value
         widget = cls.widget_from_single_value(abbrev)
@@ -341,6 +350,22 @@ def widget_from_single_value(o):
         else:
             return None
 
+    @staticmethod
+    def widget_from_annotation(t):
+        """Make widgets from type annotation and optional default value."""
+        if t is str:
+            return Text()
+        elif t is bool:
+            return Checkbox()
+        elif t in {int, Integral}:
+            return IntText()
+        elif t in {float, Real}:
+            return FloatText()
+        elif isinstance(t, EnumType):
+            return Dropdown(options={option.name: option for option in t})
+        else:
+            return None
+
     @staticmethod
     def widget_from_tuple(o):
         """Make widgets from a tuple abbreviation."""

python/ipywidgets/ipywidgets/widgets/tests/test_interaction.py

@@ -6,6 +6,7 @@
 from unittest.mock import patch
 
 import os
+from enum import Enum
 from collections import OrderedDict
 import pytest
 
@@ -22,6 +23,17 @@
 def f(**kwargs):
     pass
 
+
+class Color(Enum):
+    red = 0
+    green = 1
+    blue = 2
+
+
+def g(a: str, b: bool, c: int, d: float, e: Color) -> None:
+    pass
+
+
 displayed = []
 @pytest.fixture()
 def clear_display():
@@ -622,3 +634,27 @@ def test_state_schema():
     with open(os.path.join(os.path.dirname(os.path.realpath(__file__)), '../../', 'state.schema.json')) as f:
         schema = json.load(f)
     jsonschema.validate(state, schema)
+
+def test_type_hints():
+    c = interactive(g)
+
+    assert len(c.children) == 6
+
+    check_widget_children(
+        c,
+        a={'cls': widgets.Text},
+        b={'cls': widgets.Checkbox},
+        c={'cls': widgets.IntText},
+        d={'cls': widgets.FloatText},
+        e={
+            'cls': widgets.Dropdown,
+            'options': {
+                'red': Color.red,
+                'green': Color.green,
+                'blue': Color.blue,
+            },
+            '_options_labels': ("red", "green", "blue"),
+            '_options_values': (Color.red, Color.green, Color.blue),
+        },
+    )
+