array_tutorial.ipynb

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   "source": [
    "# array index examples"
   ]
  },
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   "source": [
    "## basic operations"
   ]
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   "source": [
    "### define an empty array"
   ]
  },
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   "source": [
    "a = [1,2,3,4,5,6,7,8,9]"
   ]
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   "source": [
    "### simplest array print"
   ]
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   "outputs": [
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     "data": {
      "text/plain": [
       "[1, 2, 3, 4, 5, 6, 7, 8, 9]"
      ]
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   "source": [
    "a"
   ]
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   "cell_type": "markdown",
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   "source": [
    "### simplest array index"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
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   "outputs": [
    {
     "data": {
      "text/plain": [
       "4"
      ]
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     "execution_count": 4,
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   "source": [
    "a[3]"
   ]
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   "source": [
    "### from the first(0) one to the third(2) one"
   ]
  },
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   "execution_count": 5,
   "metadata": {
    "scrolled": false
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   "outputs": [
    {
     "data": {
      "text/plain": [
       "[1, 2, 3]"
      ]
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     "execution_count": 5,
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   "source": [
    "a[0:3]"
   ]
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   "metadata": {},
   "source": [
    "### the third(2) one to the first one, since the step length is 1, no element is selected"
   ]
  },
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   "cell_type": "code",
   "execution_count": 6,
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   "outputs": [
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     "data": {
      "text/plain": [
       "[]"
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   ],
   "source": [
    "a[3:0]"
   ]
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   "source": [
    "## to the end"
   ]
  },
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   "metadata": {},
   "source": [
    "### from the fourth(3) position to the last postion"
   ]
  },
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   "cell_type": "code",
   "execution_count": 7,
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   "outputs": [
    {
     "data": {
      "text/plain": [
       "[4, 5, 6, 7, 8, 9]"
      ]
     },
     "execution_count": 7,
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   ],
   "source": [
    "a[3:]"
   ]
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   "metadata": {},
   "source": [
    "### from the first(0) postion to the third position"
   ]
  },
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   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[1, 2, 3]"
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     "execution_count": 8,
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   ],
   "source": [
    "a[:3]"
   ]
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## negative index"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### from the last third to end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[7, 8, 9]"
      ]
     },
     "execution_count": 9,
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   ],
   "source": [
    "a[-3:]"
   ]
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   "metadata": {},
   "source": [
    "### from the first to last fourth"
   ]
  },
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   "execution_count": 10,
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    "scrolled": true
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     "data": {
      "text/plain": [
       "[1, 2, 3, 4, 5, 6]"
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   "source": [
    "a[:-3]"
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   "source": [
    "## step length"
   ]
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   "metadata": {},
   "source": [
    "### step length = 1"
   ]
  },
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   "cell_type": "code",
   "execution_count": 11,
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     "data": {
      "text/plain": [
       "[1, 2, 3, 4, 5, 6, 7, 8, 9]"
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     "execution_count": 11,
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   "source": [
    "a[::1]"
   ]
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   "source": [
    "### step length = 2"
   ]
  },
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   "cell_type": "code",
   "execution_count": 12,
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   "outputs": [
    {
     "data": {
      "text/plain": [
       "[1, 3, 5, 7, 9]"
      ]
     },
     "execution_count": 12,
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   "source": [
    "a[::2]"
   ]
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   "metadata": {},
   "source": [
    "### step length = -2"
   ]
  },
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   "cell_type": "code",
   "execution_count": 13,
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   "outputs": [
    {
     "data": {
      "text/plain": [
       "[9, 7, 5, 3, 1]"
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   "source": [
    "a[::-2]"
   ]
  },
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## put everything together"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### same as a[0:3]"
   ]
  },
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   "cell_type": "code",
   "execution_count": 14,
   "metadata": {
    "scrolled": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[1, 2, 3]"
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     "execution_count": 14,
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   ],
   "source": [
    "a[0:3:1]"
   ]
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### from the fourth(3) to second(1) with step -1"
   ]
  },
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   "cell_type": "code",
   "execution_count": 15,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[4, 3, 2]"
      ]
     },
     "execution_count": 15,
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     "output_type": "execute_result"
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   ],
   "source": [
    "a[3:0:-1]"
   ]
  },
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   "metadata": {},
   "source": [
    "### from third(2) to seventh(6) with step 2"
   ]
  },
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   "cell_type": "code",
   "execution_count": 16,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[3, 5, 7]"
      ]
     },
     "execution_count": 16,
     "metadata": {},
     "output_type": "execute_result"
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   ],
   "source": [
    "a[2:7:2]"
   ]
  },
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### from third to seventh with step 3"
   ]
  },
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   "cell_type": "code",
   "execution_count": 17,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[3, 6]"
      ]
     },
     "execution_count": 17,
     "metadata": {},
     "output_type": "execute_result"
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   ],
   "source": [
    "a[2:7:3]"
   ]
  },
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### from eighth to fourth with step -3"
   ]
  },
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   "cell_type": "code",
   "execution_count": 18,
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   "outputs": [
    {
     "data": {
      "text/plain": [
       "[8, 5]"
      ]
     },
     "execution_count": 18,
     "metadata": {},
     "output_type": "execute_result"
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   "source": [
    "a[7:2:-3]"
   ]
  },
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   "cell_type": "code",
   "execution_count": 19,
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    {
     "data": {
      "text/plain": [
       "[9, 5]"
      ]
     },
     "execution_count": 19,
     "metadata": {},
     "output_type": "execute_result"
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   "source": [
    "a[8:1:-4]"
   ]
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   "cell_type": "code",
   "execution_count": null,
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   "outputs": [],
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