{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Updatable Displays\n",
    "\n",
    "Note: This feature requires notebook >= 5.0 or JupyterLab, and \n",
    "\n",
    "\n",
    "IPython 6 implements a new API as part of the Jupyter Protocol version 5.1 for easily updating displays.\n",
    "\n",
    "When you display something, you can now pass a `display_id` argument to attach an id to that output.\n",
    "\n",
    "Any future display with the same ID will also update other displays that had the same ID.\n",
    "\n",
    "`display` with a `display_id` will return a `DisplayHandle`\n",
    "object, which gives you easy access to update the output:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "from IPython.display import display, update_display"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'z'"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    },
    {
     "data": {
      "text/plain": [
       "<DisplayHandle display_id=update-me>"
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "handle = display('x', display_id='update-me')\n",
    "handle"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "When we call `handle.display('y')`, we get a new display of 'y',\n",
    "but in addition to that, we updated the previous display."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'z'"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "handle.display('y')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "We can also *just* update the existing displays,\n",
    "without creating a new display:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [],
   "source": [
    "handle.update('z')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "You don't have to generate display_ids yourself,\n",
    "if you specify `display_id=True`, then a unique ID will be assigned:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'hello'"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    },
    {
     "data": {
      "text/plain": [
       "<DisplayHandle display_id=118a56127f42348f8893440da7181c57>"
      ]
     },
     "execution_count": 5,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "handle = display(\"hello\", display_id=True)\n",
    "handle"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Calling `handle.display(obj)` is the same as calling `display(obj, handle.display_id)`,\n",
    "so you don't need to use the handle objects if you don't want to:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'z'"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "display('x', display_id='here');"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'z'"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "display('y', display_id='here');"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "And just like `display`, there is now `update_display`,\n",
    "which is what `DisplayHandle.update` calls:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [],
   "source": [
    "update_display('z', display_id='here')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## More detailed example\n",
    "\n",
    "One of the motivating use cases for this is simple progress bars.\n",
    "\n",
    "Here is an example ProgressBar using these APIs:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<progress style='width:60ex' max='10' value='10'></progress>"
      ],
      "text/plain": [
       "[============================================================] 10/10"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "from IPython.display import ProgressBar\n",
    "\n",
    "bar = ProgressBar(10)\n",
    "bar.display()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "And the ProgressBar has `.display` and `.update` methods:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<progress style='width:60ex' max='10' value='10'></progress>"
      ],
      "text/plain": [
       "[============================================================] 10/10"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "import time\n",
    "\n",
    "bar.display()\n",
    "\n",
    "for i in range(11):\n",
    "    bar.progress = i\n",
    "    bar.update()\n",
    "    time.sleep(0.25)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The ProgressBar also has an update built into iteration:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<progress style='width:60ex' max='10' value='10'></progress>"
      ],
      "text/plain": [
       "[============================================================] 10/10"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "for i in ProgressBar(10):\n",
    "    time.sleep(0.25)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "We would encourage any updatable-display objects that track their own display_ids to follow-suit with `.display()` and `.update()` or `.update_display()` methods."
   ]
  }
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