Add 'on_demand' option to interact() so that long-running functions can be started only when explicitly requested

IPython/html/widgets/interaction.py

@@ -1,257 +1,269 b''
 """Interact with functions using widgets."""
 
 #-----------------------------------------------------------------------------
 # Copyright (c) 2013, the IPython Development Team.
 #
 # Distributed under the terms of the Modified BSD License.
 #
 # The full license is in the file COPYING.txt, distributed with this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 from __future__ import print_function
 
 try:  # Python >= 3.3
     from inspect import signature, Parameter
 except ImportError:
     from IPython.utils.signatures import signature, Parameter
 from inspect import getcallargs
 
 from IPython.core.getipython import get_ipython
 from IPython.html.widgets import (Widget, TextWidget,
     FloatSliderWidget, IntSliderWidget, CheckboxWidget, DropdownWidget,
-    ContainerWidget, DOMWidget)
+    ContainerWidget, DOMWidget, ButtonWidget)
 from IPython.display import display, clear_output
 from IPython.utils.py3compat import string_types, unicode_type
 from IPython.utils.traitlets import HasTraits, Any, Unicode
 
 empty = Parameter.empty
 
 #-----------------------------------------------------------------------------
 # Classes and Functions
 #-----------------------------------------------------------------------------
 
 
 def _matches(o, pattern):
     """Match a pattern of types in a sequence."""
     if not len(o) == len(pattern):
         return False
     comps = zip(o,pattern)
     return all(isinstance(obj,kind) for obj,kind in comps)
 
 
 def _get_min_max_value(min, max, value=None, step=None):
     """Return min, max, value given input values with possible None."""
     if value is None:
         if not max > min:
             raise ValueError('max must be greater than min: (min={0}, max={1})'.format(min, max))
         value = min + abs(min-max)/2
         value = type(min)(value)
     elif min is None and max is None:
         if value == 0.0:
             min, max, value = 0.0, 1.0, 0.5
         elif value == 0:
             min, max, value = 0, 1, 0
         elif isinstance(value, (int, float)):
             min, max = (-value, 3*value) if value > 0 else (3*value, -value)
         else:
             raise TypeError('expected a number, got: %r' % value)
     else:
         raise ValueError('unable to infer range, value from: ({0}, {1}, {2})'.format(min, max, value))
     if step is not None:
         # ensure value is on a step
         r = (value - min) % step
         value = value - r
     return min, max, value
 
 def _widget_abbrev_single_value(o):
     """Make widgets from single values, which can be used as parameter defaults."""
     if isinstance(o, string_types):
         return TextWidget(value=unicode_type(o))
     elif isinstance(o, dict):
         return DropdownWidget(values=o)
     elif isinstance(o, bool):
         return CheckboxWidget(value=o)
     elif isinstance(o, float):
         min, max, value = _get_min_max_value(None, None, o)
         return FloatSliderWidget(value=o, min=min, max=max)
     elif isinstance(o, int):
         min, max, value = _get_min_max_value(None, None, o)
         return IntSliderWidget(value=o, min=min, max=max)
     else:
         return None
 
 def _widget_abbrev(o):
     """Make widgets from abbreviations: single values, lists or tuples."""
     float_or_int = (float, int)
     if isinstance(o, (list, tuple)):
         if o and all(isinstance(x, string_types) for x in o):
             return DropdownWidget(values=[unicode_type(k) for k in o])
         elif _matches(o, (float_or_int, float_or_int)):
             min, max, value = _get_min_max_value(o[0], o[1])
             if all(isinstance(_, int) for _ in o):
                 cls = IntSliderWidget
             else:
                 cls = FloatSliderWidget
             return cls(value=value, min=min, max=max)
         elif _matches(o, (float_or_int, float_or_int, float_or_int)):
             step = o[2]
             if step <= 0:
                 raise ValueError("step must be >= 0, not %r" % step)
             min, max, value = _get_min_max_value(o[0], o[1], step=step)
             if all(isinstance(_, int) for _ in o):
                 cls = IntSliderWidget
             else:
                 cls = FloatSliderWidget
             return cls(value=value, min=min, max=max, step=step)
     else:
         return _widget_abbrev_single_value(o)
 
 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,
         # set the initial value from the default
         try:
             widget.value = default
         except Exception:
             # ignore failure to set default
             pass
     if widget is None:
         raise ValueError("%r cannot be transformed to a Widget" % (abbrev,))
     return widget
 
 def _yield_abbreviations_for_parameter(param, kwargs):
     """Get an abbreviation for a function parameter."""
     name = param.name
     kind = param.kind
     ann = param.annotation
     default = param.default
     not_found = (name, empty, empty)
     if kind in (Parameter.POSITIONAL_OR_KEYWORD, Parameter.KEYWORD_ONLY):
         if name in kwargs:
             value = kwargs.pop(name)
         elif ann is not empty:
             value = ann
         elif default is not empty:
             value = default
         else:
             yield not_found
         yield (name, value, default)
     elif kind == Parameter.VAR_KEYWORD:
         # In this case name=kwargs and we yield the items in kwargs with their keys.
         for k, v in kwargs.copy().items():
             kwargs.pop(k)
             yield k, v, empty
 
 def _find_abbreviations(f, kwargs):
     """Find the abbreviations for a function and kwargs passed to interact."""
     new_kwargs = []
     for param in signature(f).parameters.values():
         for name, value, default in _yield_abbreviations_for_parameter(param, kwargs):
             if value is empty:
                 raise ValueError('cannot find widget or abbreviation for argument: {!r}'.format(name))
             new_kwargs.append((name, value, default))
     return new_kwargs
 
 def _widgets_from_abbreviations(seq):
     """Given a sequence of (name, abbrev) tuples, return a sequence of Widgets."""
     result = []
     for name, abbrev, default in seq:
         widget = _widget_from_abbrev(abbrev, default)
         if not widget.description:
             widget.description = name
         result.append(widget)
     return result
 
 def interactive(__interact_f, **kwargs):
     """Build a group of widgets to interact with a function."""
     f = __interact_f
     co = kwargs.pop('clear_output', True)
+    on_demand = kwargs.pop('on_demand', False)
     kwargs_widgets = []
     container = ContainerWidget()
     container.result = None
     container.args = []
     container.kwargs = dict()
     kwargs = kwargs.copy()
 
     new_kwargs = _find_abbreviations(f, kwargs)
     # Before we proceed, let's make sure that the user has passed a set of args+kwargs
     # that will lead to a valid call of the function. This protects against unspecified
     # and doubly-specified arguments.
     getcallargs(f, **{n:v for n,v,_ in new_kwargs})
     # Now build the widgets from the abbreviations.
     kwargs_widgets.extend(_widgets_from_abbreviations(new_kwargs))
 
     # This has to be done as an assignment, not using container.children.append,
     # 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 on_demand:
+        on_demand_button = ButtonWidget(description="Run %s" % f.__name__)
+        c.append(on_demand_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)
         try:
             container.result = f(**container.kwargs)
         except Exception as e:
             ip = get_ipython()
             if ip is None:
                 container.log.warn("Exception in interact callback: %s", e, exc_info=True)
             else:
                 ip.showtraceback()
 
     # Wire up the widgets
-    for widget in kwargs_widgets:
-        widget.on_trait_change(call_f, 'value')
+    # If we are doing on demand 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 on_demand:
+        on_demand_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:
         # This branch handles the cases:
         # 1. interact(f, **kwargs)
         # 2. @interact
         #    def f(*args, **kwargs):
         #        ...
         f = __interact_f
         w = interactive(f, **kwargs)
         f.widget = w
         display(w)
         return f
     else:
         # This branch handles the case:
         # @interact(a=30, b=40)
         # def f(*args, **kwargs):
         #     ...
         def dec(f):
             w = interactive(f, **kwargs)
             f.widget = w
             display(w)
             return f
         return dec
 
 class fixed(HasTraits):
     """A pseudo-widget whose value is fixed and never synced to the client."""
     value = Any(help="Any Python object")
     description = Unicode('', help="Any Python object")
     def __init__(self, value, **kwargs):
         super(fixed, self).__init__(value=value, **kwargs)