coroutines.ipynb

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   "cell_type": "markdown",
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   "source": [
    "# basic behavior of a generator used as a coroutine"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "def simple_coroutine():\n",
    "    print('-> coroutine started.')\n",
    "    x = yield\n",
    "    print('-> coroutine received.',x)\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "<generator object simple_coroutine at 0x7fa24119d0d0>"
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "my_coro = simple_coroutine()\n",
    "my_coro"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "-> coroutine started.\n"
     ]
    }
   ],
   "source": [
    "next(my_coro)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "-> coroutine received. 110\n"
     ]
    },
    {
     "ename": "StopIteration",
     "evalue": "",
     "output_type": "error",
     "traceback": [
      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[0;31mStopIteration\u001b[0m                             Traceback (most recent call last)",
      "\u001b[0;32m<ipython-input-5-2c0aff799e43>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mmy_coro\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0msend\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;36m110\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[0;31mStopIteration\u001b[0m: "
     ]
    }
   ],
   "source": [
    "my_coro.send(110)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# coroutine\n",
    "> A coroutine can be in one of four states.You can determine the current state using the inspect.getgeneratorstate(...) function which returns one of these strings:\n",
    "> - 'GEN_CREATE'    -> waiting to execution\n",
    "> - 'GEN_RUNNING'   -> Currently being executed by the interpreter\n",
    "> - 'GEN_SUSPENDED' -> Currently suspended at a yield expression\n",
    "> - 'GEN_CLOSEd'    -> execution has completed"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {},
   "outputs": [],
   "source": [
    "# Example\n",
    "# coroutine to compute a running average\n",
    "\n",
    "def coro_average():\n",
    "    total = 0.0\n",
    "    count = 0\n",
    "    average = None\n",
    "#     x = None\n",
    "    \n",
    "    while True:\n",
    "        term = yield  average # why average\n",
    "        total += term\n",
    "        count += 1\n",
    "        average = total/count\n",
    "        \n",
    "coro_avg = coro_average()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "metadata": {},
   "outputs": [],
   "source": [
    "next(coro_avg) # prime it by calling next"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "10.0"
      ]
     },
     "execution_count": 16,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "coro_avg.send(10)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "29.0"
      ]
     },
     "execution_count": 17,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "coro_avg.send(48)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# returning a value from a coroutine"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 20,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "Result(count=3, average=15.5)"
      ]
     },
     "execution_count": 20,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "from collections import namedtuple\n",
    "\n",
    "Result = namedtuple('Result', 'count average')\n",
    "\n",
    "def coro_average():\n",
    "    total = 0.0\n",
    "    count = 0\n",
    "    average = None\n",
    "    \n",
    "    while True:\n",
    "        term = yield  # why average\n",
    "        if term is None:\n",
    "            break\n",
    "        total += term\n",
    "        count += 1\n",
    "        average = total/count\n",
    "    return Result(count,average)\n",
    "\n",
    "coro_avg = coro_average()\n",
    "next(coro_avg)\n",
    "coro_avg.send(10)\n",
    "\n",
    "coro_avg.send(30)\n",
    "coro_avg.send(6.5)\n",
    "# coro_avg.send(None)\n",
    "try:\n",
    "    coro_avg.send(None)\n",
    "except StopIteration as exc:\n",
    "    result = exc.value\n",
    "result"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Using ***yield from***"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 21,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['A', 'B', 0, 1, 2]"
      ]
     },
     "execution_count": 21,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "def gen():\n",
    "    yield from 'AB'\n",
    "    yield from range(3)\n",
    "    \n",
    "list(gen())"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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