{ "metadata": { "cell_tags": [ [ "", null ] ], "name": "" }, "nbformat": 3, "nbformat_minor": 0, "worksheets": [ { "cells": [ { "cell_type": "code", "collapsed": false, "input": [ "from IPython.html import widgets # Widget definitions\n", "from IPython.display import display # Used to display widgets in the notebook" ], "language": "python", "metadata": {}, "outputs": [], "prompt_number": 1 }, { "cell_type": "heading", "level": 1, "metadata": {}, "source": [ "Traitlet Events" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "The widget properties are IPython traitlets. Traitlets are eventful. To handle property value changes, the `on_trait_change` method of the widget can be used to register an event handling callback. The doc string for `on_trait_change` can be seen below. Both the `name` and `remove` properties are optional." ] }, { "cell_type": "code", "collapsed": false, "input": [ "print(widgets.Widget.on_trait_change.__doc__)" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "Setup a handler to be called when a trait changes.\n", "\n", " This is used to setup dynamic notifications of trait changes.\n", "\n", " Static handlers can be created by creating methods on a HasTraits\n", " subclass with the naming convention '_[traitname]_changed'. Thus,\n", " to create static handler for the trait 'a', create the method\n", " _a_changed(self, name, old, new) (fewer arguments can be used, see\n", " below).\n", "\n", " Parameters\n", " ----------\n", " handler : callable\n", " A callable that is called when a trait changes. Its\n", " signature can be handler(), handler(name), handler(name, new)\n", " or handler(name, old, new).\n", " name : list, str, None\n", " If None, the handler will apply to all traits. If a list\n", " of str, handler will apply to all names in the list. If a\n", " str, the handler will apply just to that name.\n", " remove : bool\n", " If False (the default), then install the handler. If True\n", " then unintall it.\n", " \n" ] } ], "prompt_number": 2 }, { "cell_type": "markdown", "metadata": {}, "source": [ "Mentioned in the doc string, the callback registered can have 4 possible signatures:\n", "\n", "- callback()\n", "- callback(trait_name)\n", "- callback(trait_name, new_value)\n", "- callback(trait_name, old_value, new_value)\n", "\n", "An example of how to output an IntRangeWiget's value as it is changed can be seen below." ] }, { "cell_type": "code", "collapsed": false, "input": [ "intrange = widgets.IntRangeWidget()\n", "display(intrange)\n", "\n", "def on_value_change(name, value):\n", " print value\n", "\n", "intrange.on_trait_change(on_value_change, 'value')" ], "language": "python", "metadata": {}, "outputs": [], "prompt_number": 3 }, { "cell_type": "heading", "level": 1, "metadata": {}, "source": [ "Specialized Events" ] }, { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Button On Click Event" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "The `ButtonWidget` is a special widget, like the `ContainerWidget` and `MulticontainerWidget`, that isn't used to represent a data type. Instead the button widget is used to handle mouse clicks. The `on_click` method of the `ButtonWidget` can be used to register a click even handler. The doc string of the `on_click` can be seen below." ] }, { "cell_type": "code", "collapsed": false, "input": [ "print(widgets.ButtonWidget.on_click.__doc__)" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "Register a callback to execute when the button is clicked. The\n", " callback can either accept no parameters or one sender parameter:\n", " - callback()\n", " - callback(sender)\n", " If the callback has a sender parameter, the ButtonWidget instance that\n", " called the callback will be passed into the method as the sender.\n", "\n", " Parameters\n", " ----------\n", " remove : bool (optional)\n", " Set to true to remove the callback from the list of callbacks.\n" ] } ], "prompt_number": 4 }, { "cell_type": "markdown", "metadata": {}, "source": [ "Button clicks are tracked by the `clicks` property of the button widget. By using the `on_click` method and the `clicks` property, a button that outputs how many times it has been clicked is shown below." ] }, { "cell_type": "code", "collapsed": false, "input": [ "button = widgets.ButtonWidget(description=\"Click Me!\")\n", "display(button)\n", "\n", "def on_button_clicked(sender):\n", " print(\"Button clicked %d times.\" % sender.clicks)\n", "\n", "button.on_click(on_button_clicked)" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "Button clicked 1 times.\n" ] }, { "output_type": "stream", "stream": "stdout", "text": [ "Button clicked 2 times.\n" ] }, { "output_type": "stream", "stream": "stdout", "text": [ "Button clicked 3 times.\n" ] } ], "prompt_number": 5 }, { "cell_type": "markdown", "metadata": {}, "source": [ "Event handlers can also be used to create widgets. In the example below, clicking a button spawns another button with a description equal to how many times the parent button had been clicked at the time." ] }, { "cell_type": "code", "collapsed": false, "input": [ "def show_button(sender=None):\n", " button = widgets.ButtonWidget()\n", " button.description = \"%d\" % (sender.clicks if sender is not None else 0)\n", " display(button)\n", " button.on_click(show_button)\n", "show_button()\n", " " ], "language": "python", "metadata": {}, "outputs": [], "prompt_number": 6 } ], "metadata": {} } ] }