Merge pull request #6051 from chronitis/interact-widget-on-demand

Interact on_demand option

IPython/html/widgets/__init__.py

@@ -9,7 +9,7 @@ from .widget_int import IntText, BoundedIntText, IntSlider, IntProgress, IntRang
 from .widget_selection import RadioButtons, ToggleButtons, Dropdown, Select
 from .widget_selectioncontainer import Tab, Accordion
 from .widget_string import HTML, Latex, Text, Textarea
-from .interaction import interact, interactive, fixed
+from .interaction import interact, interactive, fixed, interact_manual
 
 # Deprecated classes
 from .widget_bool import CheckboxWidget, ToggleButtonWidget

IPython/html/widgets/interaction.py

@@ -23,7 +23,7 @@ from inspect import getcallargs
 from IPython.core.getipython import get_ipython
 from IPython.html.widgets import (Widget, Text,
     FloatSlider, IntSlider, Checkbox, Dropdown,
-    Box, DOMWidget)
+    Box, Button, DOMWidget)
 from IPython.display import display, clear_output
 from IPython.utils.py3compat import string_types, unicode_type
 from IPython.utils.traitlets import HasTraits, Any, Unicode
@@ -114,7 +114,7 @@ def _widget_from_abbrev(abbrev, default=empty):
     """Build a Widget instance given an abbreviation or Widget."""
     if isinstance(abbrev, Widget) or isinstance(abbrev, fixed):
         return abbrev
-    
+
     widget = _widget_abbrev(abbrev)
     if default is not empty and isinstance(abbrev, (list, tuple, dict)):
         # if it's not a single-value abbreviation,
@@ -175,6 +175,7 @@ def interactive(__interact_f, **kwargs):
     """Build a group of widgets to interact with a function."""
     f = __interact_f
     co = kwargs.pop('clear_output', True)
+    manual = kwargs.pop('__manual', False)
     kwargs_widgets = []
     container = Box()
     container.result = None
@@ -194,16 +195,23 @@ def interactive(__interact_f, **kwargs):
     # so that traitlets notices the update. We skip any objects (such as fixed) that
     # are not DOMWidgets.
     c = [w for w in kwargs_widgets if isinstance(w, DOMWidget)]
+
+    # If we are only to run the function on demand, add a button to request this
+    if manual:
+        manual_button = Button(description="Run %s" % f.__name__)
+        c.append(manual_button)
     container.children = c
 
     # Build the callback
-    def call_f(name, old, new):
+    def call_f(name=None, old=None, new=None):
         container.kwargs = {}
         for widget in kwargs_widgets:
             value = widget.value
             container.kwargs[widget.description] = value
         if co:
             clear_output(wait=True)
+        if manual:
+            manual_button.disabled = True
         try:
             container.result = f(**container.kwargs)
         except Exception as e:
@@ -212,18 +220,27 @@ def interactive(__interact_f, **kwargs):
                 container.log.warn("Exception in interact callback: %s", e, exc_info=True)
             else:
                 ip.showtraceback()
+        finally:
+            if manual:
+                manual_button.disabled = False
 
     # Wire up the widgets
-    for widget in kwargs_widgets:
-        widget.on_trait_change(call_f, 'value')
+    # If we are doing manual running, the callback is only triggered by the button
+    # Otherwise, it is triggered for every trait change received
+    # On-demand running also suppresses running the fucntion with the initial parameters
+    if manual:
+        manual_button.on_click(call_f)
+    else:
+        for widget in kwargs_widgets:
+            widget.on_trait_change(call_f, 'value')
 
-    container.on_displayed(lambda _: call_f(None, None, None))
+        container.on_displayed(lambda _: call_f(None, None, None))
 
     return container
 
 def interact(__interact_f=None, **kwargs):
     """interact(f, **kwargs)
-    
+
     Interact with a function using widgets."""
     # positional arg support in: https://gist.github.com/8851331
     if __interact_f is not None:
@@ -249,6 +266,16 @@ def interact(__interact_f=None, **kwargs):
             return f
         return dec
 
+def interact_manual(__interact_f=None, **kwargs):
+    """interact_manual(f, **kwargs)
+    
+    As `interact()`, generates widgets for each argument, but rather than running
+    the function after each widget change, adds a "Run" button and waits for it
+    to be clicked. Useful if the function is long-running and has several
+    parameters to change.
+    """
+    return interact(__interact_f, __manual=True, **kwargs)
+
 class fixed(HasTraits):
     """A pseudo-widget whose value is fixed and never synced to the client."""
     value = Any(help="Any Python object")

IPython/html/widgets/tests/test_interaction.py

@@ -481,6 +481,19 @@ def test_custom_description():
         description='foo',
     )
 
+def test_interact_manual_button():
+    c = interactive(f, __manual=True)
+    w = c.children[0]
+    check_widget(w, cls=widgets.Button)
+
+def test_interact_manual_nocall():
+    callcount = 0
+    def calltest(testarg):
+        callcount += 1
+    c = interactive(calltest, testarg=5, __manual=True)
+    c.children[0].value = 10
+    nt.assert_equal(callcount, 0)
+
 def test_int_range_logic():
     irsw = widgets.IntRangeSlider
     w = irsw(value=(2, 4), min=0, max=6)