Why Python's 3.x's "yield from" is useful

yield_from.ipynb

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   "source": [
    "# Why 'yield from' is Useful"
   ]
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   "source": [
    "Lets say you have a generator, `foo()`, that needs to present data from a another generator, `bar()`. One might naively yield the sub-generator:"
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    "def foo():\n",
    "    yield 1\n",
    "    yield 2\n",
    "    yield bar()\n",
    "\n",
    "def bar():\n",
    "    yield 3\n",
    "    yield 4"
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       "[1, 2, <generator object bar at 0x7fc29017eaf8>]"
      ]
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     "execution_count": 13,
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   "source": [
    "list(foo())"
   ]
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   "source": [
    "Oh no! There's a generator in my list"
   ]
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   "cell_type": "markdown",
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   "source": [
    "# Enter 'yield from'"
   ]
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       "[1, 2, 3, 4]"
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     "execution_count": 17,
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   "source": [
    "def foo():\n",
    "    yield 1\n",
    "    yield 2\n",
    "    yield from bar()\n",
    "\n",
    "def bar():\n",
    "    yield 3\n",
    "    yield 4\n",
    "    \n",
    "list(foo())"
   ]
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   "source": [
    "Much better"
   ]
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# In a World Without 'yield from' (Python 2.7)\n",
    "\n",
    "To get the same behavior without yield from you must delegate iteration to the parent generator"
   ]
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     "data": {
      "text/plain": [
       "[1, 2, 3, 4]"
      ]
     },
     "execution_count": 15,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "def foo():\n",
    "    yield 1\n",
    "    yield 2\n",
    "    for elem in bar():\n",
    "        yield elem\n",
    "\n",
    "def bar():\n",
    "    yield 3\n",
    "    yield 4\n",
    "    \n",
    "list(foo())"
   ]
  }
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