python3_lambda.ipynb

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   "source": [
    "# Lambda Function"
   ]
  },
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Why Lambda ?\n",
    "\n",
    "- lambda 是個匿名函數 (anonymous function), 在程式碼上可以更優雅, 簡化繁瑣步驟\n",
    "- can take any number of arguments, but can only have one expression\n",
    "- 使用Function的主要目的為 ：\n",
    "    1. 降低重複的code\n",
    "    2. 模組化\n",
    "    - 而當你不需要給予一個function名字時 (anonymous function), 則可以使用lambda"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Basic Usage"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### One argument"
   ]
  },
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   "cell_type": "code",
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    "ExecuteTime": {
     "end_time": "2018-12-02T12:30:43.197917Z",
     "start_time": "2018-12-02T12:30:43.194064Z"
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   "outputs": [
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     "text": [
      "15\n"
     ]
    }
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   "source": [
    "x = lambda a : a + 10\n",
    "print(x(5));"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Multiplies argument"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
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     "text": [
      "13\n"
     ]
    }
   ],
   "source": [
    " x = lambda a, b, c : a + b + c\n",
    "print(x(5, 6, 2)) "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Conditional statement"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 19,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "11\n"
     ]
    }
   ],
   "source": [
    "f = lambda x:  x if(x > 10) else x^2\n",
    "print(f(9))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Lambda in Function"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "22\n"
     ]
    }
   ],
   "source": [
    "def myfunc(n):\n",
    "  return lambda a : a * n\n",
    "\n",
    "mydoubler = myfunc(2)\n",
    "\n",
    "print(mydoubler(11))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Advanced Usage"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Combined with filter"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[5, 7, 97, 77, 23, 73, 61]\n"
     ]
    }
   ],
   "source": [
    "li = [5, 7, 22, 97, 54, 62, 77, 23, 73, 61] \n",
    "final_list = list(filter(lambda x: (x%2 != 0) , li)) \n",
    "print(final_list) "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Combined with map"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[10, 14, 44, 194, 108, 124, 154, 46, 146, 122]\n"
     ]
    }
   ],
   "source": [
    "li = [5, 7, 22, 97, 54, 62, 77, 23, 73, 61] \n",
    "final_list = list(map(lambda x: x*2 , li)) \n",
    "print(final_list) "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Combined with reduced "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "193\n"
     ]
    }
   ],
   "source": [
    "from functools import reduce\n",
    "li = [5, 8, 10, 20, 50, 100] \n",
    "sum = reduce((lambda x, y: x + y), li) \n",
    "print (sum)  #(5+8+10+20+50+100)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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