{
 "cells": [
  {
   "cell_type": "markdown",
   "id": "aed0888f",
   "metadata": {},
   "source": [
    "## Nested Lists"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "22f767f2",
   "metadata": {},
   "source": [
    "Lists can contain anything, including other lists!"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "c6f5cf8e",
   "metadata": {},
   "outputs": [],
   "source": [
    "grid = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]\n",
    "print(grid)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "015139e0",
   "metadata": {},
   "source": [
    "If given `a = [1, 2, 3]` and doing `a[0]` gives you the first thing in the list (in this case, a number, `1`), what do you think doing `grid[0]` evaluates to?\n",
    "\n",
    "Recall that when figuring out what a line of code evaluates to, we can iteratively evaluate sub-expressions. So, `a[0]` is then equivalent to `[1, 2, 3][0]`, which is then equivalent to `1`.\n",
    "\n",
    "As such, `grid[0]` is equivalent to `[[1, 2, 3], [4, 5, 6], [7, 8, 9]][0]`, which then becomes `[1, 2, 3]`:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "bf1ec75d",
   "metadata": {},
   "outputs": [],
   "source": [
    "grid = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]\n",
    "grid[0]"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "4d25a37a",
   "metadata": {},
   "source": [
    "If, therefore, we have an expression (`grid[0]`) that evaluates to a list, we can treat it like a list! `[1, 2, 3][0]` evaluated to `1`; and so if we do `grid[0][0]`, we get the same result:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "e87a826d",
   "metadata": {},
   "outputs": [],
   "source": [
    "grid[0][0]"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "0e309b11",
   "metadata": {},
   "source": [
    "For each of the following cells, does it evaluate to something (and if so, what?), or is it an error?"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "449c3046",
   "metadata": {},
   "outputs": [],
   "source": [
    "[\"Once\", \"upon\", \"a\", \"time\"][2]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "bcc1ac1b",
   "metadata": {},
   "outputs": [],
   "source": [
    "[\"Once\", \"upon\", \"a\", \"time\"][0,2,3]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "1885242f",
   "metadata": {},
   "outputs": [],
   "source": [
    "[\"Once\", \"upon\", \"a\", \"time\"][[0,2,3]]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "e05cfaf2",
   "metadata": {},
   "outputs": [],
   "source": [
    "[\"Once\", \"upon\", \"a\", \"time\"][[0,2,3][1]]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "5293f1a9",
   "metadata": {},
   "outputs": [],
   "source": [
    "[[\"Once\", \"upon\", \"a\", \"time\"][0:2:3]]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "996a8d1e",
   "metadata": {},
   "outputs": [],
   "source": [
    "[[\"Once\", \"upon\", \"a\", \"time\"]][0:2:3][1]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "8b83343b",
   "metadata": {},
   "outputs": [],
   "source": [
    "[[[\"Once\"], \"upon\", [\"a\"], \"time\"]][0][[0,2,3][1]][0]"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "ece4fa90",
   "metadata": {},
   "source": [
    "## Nested Lists and Functions\n",
    "\n",
    "Recall when we had functions that operated on lists, where the list passed into the function was _not_ copied. Instead, a reference to the list was passed in. What happens if we do similar things with nested lists?"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "506268a7",
   "metadata": {},
   "outputs": [],
   "source": [
    "def do_stuff(nums):\n",
    "    nums[0] = []\n",
    "\n",
    "grid = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]\n",
    "do_stuff(grid)\n",
    "print(grid)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "97eefbb0",
   "metadata": {},
   "outputs": [],
   "source": [
    "def do_stuff(nums):\n",
    "    nums[0][0] = []\n",
    "\n",
    "grid = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]\n",
    "do_stuff(grid)\n",
    "print(grid)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "09fb2950",
   "metadata": {},
   "outputs": [],
   "source": [
    "def do_stuff(nums):\n",
    "    inner_list = nums[0]\n",
    "    inner_list[0] = []\n",
    "\n",
    "grid = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]\n",
    "do_stuff(grid)\n",
    "print(grid)"
   ]
  }
 ],
 "metadata": {
  "kernelspec": {
   "display_name": ".venv",
   "language": "python",
   "name": "python3"
  },
  "language_info": {
   "codemirror_mode": {
    "name": "ipython",
    "version": 3
   },
   "file_extension": ".py",
   "mimetype": "text/x-python",
   "name": "python",
   "nbconvert_exporter": "python",
   "pygments_lexer": "ipython3",
   "version": "3.13.3"
  }
 },
 "nbformat": 4,
 "nbformat_minor": 5
}