{ "cells": [ { "cell_type": "markdown", "id": "73703282", "metadata": {}, "source": [ "## Lecture 16, 09 October 2025" ] }, { "cell_type": "markdown", "id": "5a8115d2", "metadata": {}, "source": [ "### Linked lists" ] }, { "cell_type": "markdown", "id": "1dc03300-c25c-4d9b-9e0b-56293ad5cac4", "metadata": {}, "source": [ "- Our current definition, with iterative `append()`" ] }, { "cell_type": "code", "execution_count": 1, "id": "02ec7e61-dfb0-4e56-8944-1c7367a256ab", "metadata": {}, "outputs": [], "source": [ "class List:\n", " def __init__(self,initlist = []):\n", " self.value = None\n", " self.next = None\n", " for x in initlist:\n", " self.append(x)\n", " return\n", "\n", " def isempty(self):\n", " return(self.value == None)\n", " \n", " def append(self,v):\n", " if self.isempty():\n", " self.value = v\n", " return\n", " \n", " temp = self\n", " while temp.next != None:\n", " temp = temp.next\n", "\n", " temp.next = List()\n", " temp.next.value = v \n", " return \n", "\n", " def insert(self,v):\n", " if self.isempty():\n", " self.value = v\n", " return\n", "\n", " newnode = List()\n", " newnode.value = v\n", " \n", " # Exchange values in self and newnode\n", " (self.value, newnode.value) = (newnode.value, self.value)\n", "\n", " # Switch links\n", " (self.next, newnode.next) = (newnode, self.next)\n", "\n", " return\n", "\n", "\n", " def __str__(self):\n", " # Iteratively create a Python list from linked list\n", " # and convert that to a string\n", " selflist = []\n", " if self.isempty():\n", " return(str(selflist))\n", "\n", " temp = self\n", " selflist.append(temp.value)\n", " \n", " while temp.next != None:\n", " temp = temp.next\n", " selflist.append(temp.value)\n", "\n", " return(str(selflist))" ] }, { "cell_type": "markdown", "id": "f8df0586-8da7-4f78-bf75-6be3ee12a8fe", "metadata": {}, "source": [ "- Add recursive `append()`\n", " - `appendi()`, iterative\n", " - `appendr()`, recursive\n", " - Dummy `append()` that calls either `appendi()` or `appendr()`\n", " - To avoid problems with `__init__`, `__str__`" ] }, { "cell_type": "code", "execution_count": 2, "id": "85ae6403-46d8-4969-b3d6-ef836167a73c", "metadata": {}, "outputs": [], "source": [ "class List:\n", " def __init__(self,initlist = []):\n", " self.value = None\n", " self.next = None\n", " for x in initlist:\n", " self.append(x)\n", " return\n", "\n", " def isempty(self):\n", " return(self.value == None)\n", " \n", " def appendi(self,v): # append, iterative\n", " if self.isempty():\n", " self.value = v\n", " return\n", " \n", " temp = self\n", " while temp.next != None:\n", " temp = temp.next\n", "\n", " temp.next = List()\n", " temp.next.value = v \n", " return\n", "\n", " def appendr(self,v): # append, recursive\n", " if self.isempty():\n", " self.value = v\n", " elif self.next == None:\n", " self.next = List()\n", " self.next.value = v\n", " else:\n", " self.next.appendr(v)\n", " return\n", "\n", " def append(self,v): # Could point to appendi or appendr\n", " self.appendr(v)\n", " return\n", "\n", " def insert(self,v):\n", " if self.isempty():\n", " self.value = v\n", " return\n", "\n", " newnode = List()\n", " newnode.value = v\n", " \n", " # Exchange values in self and newnode\n", " (self.value, newnode.value) = (newnode.value, self.value)\n", "\n", " # Switch links\n", " (self.next, newnode.next) = (newnode, self.next)\n", "\n", " return\n", "\n", "\n", " def __str__(self):\n", " # Iteratively create a Python list from linked list\n", " # and convert that to a string\n", " selflist = []\n", " if self.isempty():\n", " return(str(selflist))\n", "\n", " temp = self\n", " selflist.append(temp.value)\n", " \n", " while temp.next != None:\n", " temp = temp.next\n", " selflist.append(temp.value)\n", "\n", " return(str(selflist))" ] }, { "cell_type": "code", "execution_count": 3, "id": "f7675182-80cc-439d-973a-551b5936df56", "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "[20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1]\n" ] } ], "source": [ "l = List()\n", "for i in range(20,0,-1):\n", " l.appendr(i)\n", "print(l)" ] }, { "cell_type": "markdown", "id": "a33fef25-8dd0-43d1-ae9a-c25914054aad", "metadata": {}, "source": [ "- Some performance measurements" ] }, { "cell_type": "code", "execution_count": 4, "id": "70b38185-0128-42e2-ba65-0aefe5b22dda", "metadata": {}, "outputs": [], "source": [ "import time" ] }, { "cell_type": "markdown", "id": "aba5d2fe-98b8-412f-9410-3a01bd848960", "metadata": {}, "source": [ "- Iterative append, quadratic complexity" ] }, { "cell_type": "code", "execution_count": 5, "id": "1fe19866", "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "1000 0.037408503994811326\n", "2000 0.13884098699782044\n", "3000 0.25658054200175684\n", "4000 0.41125536999606993\n" ] } ], "source": [ "for i in range(1,5):\n", " unit = 1000\n", " l1 = List()\n", " start = time.perf_counter()\n", " for j in range(i*unit):\n", " l1.appendi(j)\n", " elapsed = time.perf_counter() - start\n", " print(i*unit,elapsed)" ] }, { "cell_type": "markdown", "id": "9c322128-77ce-4e6c-bcc8-86e69770f842", "metadata": {}, "source": [ "- Recursive append, also quadratic, but 5x overhead due to recursive calls" ] }, { "cell_type": "code", "execution_count": 6, "id": "8275bbb5-8b08-4544-b165-dcfe064e8a8d", "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "1000 0.15295926301041618\n", "2000 0.5776570989983156\n" ] }, { "ename": "RecursionError", "evalue": "maximum recursion depth exceeded", "output_type": "error", "traceback": [ "\u001b[31m---------------------------------------------------------------------------\u001b[39m", "\u001b[31mRecursionError\u001b[39m Traceback (most recent call last)", "\u001b[36mCell\u001b[39m\u001b[36m \u001b[39m\u001b[32mIn[6]\u001b[39m\u001b[32m, line 6\u001b[39m\n\u001b[32m 4\u001b[39m start = time.perf_counter()\n\u001b[32m 5\u001b[39m \u001b[38;5;28;01mfor\u001b[39;00m j \u001b[38;5;129;01min\u001b[39;00m \u001b[38;5;28mrange\u001b[39m(i*unit):\n\u001b[32m----> \u001b[39m\u001b[32m6\u001b[39m \u001b[43ml1\u001b[49m\u001b[43m.\u001b[49m\u001b[43mappendr\u001b[49m\u001b[43m(\u001b[49m\u001b[43mj\u001b[49m\u001b[43m)\u001b[49m\n\u001b[32m 7\u001b[39m elapsed = time.perf_counter() - start\n\u001b[32m 8\u001b[39m \u001b[38;5;28mprint\u001b[39m(i*unit,elapsed)\n", "\u001b[36mCell\u001b[39m\u001b[36m \u001b[39m\u001b[32mIn[2]\u001b[39m\u001b[32m, line 32\u001b[39m, in \u001b[36mList.appendr\u001b[39m\u001b[34m(self, v)\u001b[39m\n\u001b[32m 30\u001b[39m \u001b[38;5;28mself\u001b[39m.next.value = v\n\u001b[32m 31\u001b[39m \u001b[38;5;28;01melse\u001b[39;00m:\n\u001b[32m---> \u001b[39m\u001b[32m32\u001b[39m \u001b[38;5;28;43mself\u001b[39;49m\u001b[43m.\u001b[49m\u001b[43mnext\u001b[49m\u001b[43m.\u001b[49m\u001b[43mappendr\u001b[49m\u001b[43m(\u001b[49m\u001b[43mv\u001b[49m\u001b[43m)\u001b[49m\n\u001b[32m 33\u001b[39m \u001b[38;5;28;01mreturn\u001b[39;00m\n", "\u001b[36mCell\u001b[39m\u001b[36m \u001b[39m\u001b[32mIn[2]\u001b[39m\u001b[32m, line 32\u001b[39m, in \u001b[36mList.appendr\u001b[39m\u001b[34m(self, v)\u001b[39m\n\u001b[32m 30\u001b[39m \u001b[38;5;28mself\u001b[39m.next.value = v\n\u001b[32m 31\u001b[39m \u001b[38;5;28;01melse\u001b[39;00m:\n\u001b[32m---> \u001b[39m\u001b[32m32\u001b[39m \u001b[38;5;28;43mself\u001b[39;49m\u001b[43m.\u001b[49m\u001b[43mnext\u001b[49m\u001b[43m.\u001b[49m\u001b[43mappendr\u001b[49m\u001b[43m(\u001b[49m\u001b[43mv\u001b[49m\u001b[43m)\u001b[49m\n\u001b[32m 33\u001b[39m \u001b[38;5;28;01mreturn\u001b[39;00m\n", " \u001b[31m[... skipping similar frames: List.appendr at line 32 (2973 times)]\u001b[39m\n", "\u001b[36mCell\u001b[39m\u001b[36m \u001b[39m\u001b[32mIn[2]\u001b[39m\u001b[32m, line 32\u001b[39m, in \u001b[36mList.appendr\u001b[39m\u001b[34m(self, v)\u001b[39m\n\u001b[32m 30\u001b[39m \u001b[38;5;28mself\u001b[39m.next.value = v\n\u001b[32m 31\u001b[39m \u001b[38;5;28;01melse\u001b[39;00m:\n\u001b[32m---> \u001b[39m\u001b[32m32\u001b[39m \u001b[38;5;28;43mself\u001b[39;49m\u001b[43m.\u001b[49m\u001b[43mnext\u001b[49m\u001b[43m.\u001b[49m\u001b[43mappendr\u001b[49m\u001b[43m(\u001b[49m\u001b[43mv\u001b[49m\u001b[43m)\u001b[49m\n\u001b[32m 33\u001b[39m \u001b[38;5;28;01mreturn\u001b[39;00m\n", "\u001b[36mCell\u001b[39m\u001b[36m \u001b[39m\u001b[32mIn[2]\u001b[39m\u001b[32m, line 26\u001b[39m, in \u001b[36mList.appendr\u001b[39m\u001b[34m(self, v)\u001b[39m\n\u001b[32m 25\u001b[39m \u001b[38;5;28;01mdef\u001b[39;00m\u001b[38;5;250m \u001b[39m\u001b[34mappendr\u001b[39m(\u001b[38;5;28mself\u001b[39m,v): \u001b[38;5;66;03m# append, recursive\u001b[39;00m\n\u001b[32m---> \u001b[39m\u001b[32m26\u001b[39m \u001b[38;5;28;01mif\u001b[39;00m \u001b[38;5;28;43mself\u001b[39;49m\u001b[43m.\u001b[49m\u001b[43misempty\u001b[49m\u001b[43m(\u001b[49m\u001b[43m)\u001b[49m:\n\u001b[32m 27\u001b[39m \u001b[38;5;28mself\u001b[39m.value = v\n\u001b[32m 28\u001b[39m \u001b[38;5;28;01melif\u001b[39;00m \u001b[38;5;28mself\u001b[39m.next == \u001b[38;5;28;01mNone\u001b[39;00m:\n", "\u001b[31mRecursionError\u001b[39m: maximum recursion depth exceeded" ] } ], "source": [ "for i in range(1,5):\n", " unit = 1000\n", " l1 = List()\n", " start = time.perf_counter()\n", " for j in range(i*unit):\n", " l1.appendr(j)\n", " elapsed = time.perf_counter() - start\n", " print(i*unit,elapsed)" ] }, { "cell_type": "markdown", "id": "c6e80c8b-ceb1-4373-a7ac-1cafe921d0e4", "metadata": {}, "source": [ "- Enhance recursion limit\n", " - $2^{31}-1$ is maximum allowed" ] }, { "cell_type": "code", "execution_count": 7, "id": "958b087f-76fc-43d5-baad-6e3d87b33162", "metadata": {}, "outputs": [], "source": [ "import sys\n", "sys.setrecursionlimit(2**31-1)" ] }, { "cell_type": "code", "execution_count": 8, "id": "f937d90c-598a-44ff-9769-2cce07715cc0", "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "1000 0.1520825240004342\n", "2000 0.59965024900157\n", "3000 1.326439897005912\n", "4000 2.4543402420094935\n" ] } ], "source": [ "for i in range(1,5):\n", " unit = 1000\n", " l1 = List()\n", " start = time.perf_counter()\n", " for j in range(i*unit):\n", " l1.appendr(j)\n", " elapsed = time.perf_counter() - start\n", " print(i*unit,elapsed)" ] }, { "cell_type": "markdown", "id": "a1828ac0-29f5-4b11-ab99-612e3e4c9b87", "metadata": {}, "source": [ "\n", "\n", "\n", "\n", "\n", "\n", "\n", "\n", "\n", "\n", "\n", "\n", "\n", "\n" ] }, { "cell_type": "markdown", "id": "eb79f4ef-fdce-4457-a89e-09e8e5075bac", "metadata": {}, "source": [ "- Add `delete()`" ] }, { "cell_type": "code", "execution_count": 9, "id": "86621218-ae0a-4f70-8176-bfc6dea51eda", "metadata": {}, "outputs": [], "source": [ "class List:\n", " def __init__(self,initlist = []):\n", " self.value = None\n", " self.next = None\n", " for x in initlist:\n", " self.append(x)\n", " return\n", "\n", " def isempty(self):\n", " return(self.value == None)\n", " \n", " def appendi(self,v): # append, iterative\n", " if self.isempty():\n", " self.value = v\n", " return\n", " \n", " temp = self\n", " while temp.next != None:\n", " temp = temp.next\n", "\n", " temp.next = List()\n", " temp.next.value = v \n", " return\n", "\n", " def appendr(self,v): # append, recursive\n", " if self.isempty():\n", " self.value = v\n", " elif self.next == None:\n", " self.next = List([v])\n", " else:\n", " self.next.appendr(v)\n", " return\n", "\n", " def append(self,v):\n", " self.appendr(v)\n", " return\n", "\n", " def insert(self,v):\n", " if self.isempty():\n", " self.value = v\n", " return\n", "\n", " newnode = List()\n", " newnode.value = v\n", " \n", " # Exchange values in self and newnode\n", " (self.value, newnode.value) = (newnode.value, self.value)\n", "\n", " # Switch links\n", " (self.next, newnode.next) = (newnode, self.next)\n", "\n", " return\n", "\n", " def delete(self,v): # delete, recursive\n", " if self.isempty():\n", " return\n", "\n", " if self.value == v:\n", " if self.next != None:\n", " self.value = self.next.value\n", " self.next = self.next.next\n", " else:\n", " self.value = None\n", " return\n", " else:\n", " if self.next != None:\n", " self.next.delete(v)\n", " # Ensure that there is no empty node at the end of the list\n", " if self.next.value == None:\n", " self.next = None\n", " return\n", " \n", " def __str__(self):\n", " # Iteratively create a Python list from linked list\n", " # and convert that to a string\n", " selflist = []\n", " if self.isempty():\n", " return(str(selflist))\n", "\n", " temp = self\n", " selflist.append(temp.value)\n", " \n", " while temp.next != None:\n", " temp = temp.next\n", " selflist.append(temp.value)\n", "\n", " return(str(selflist))" ] }, { "cell_type": "code", "execution_count": 10, "id": "7cef336f-2692-43f2-86c5-e2dbebc3b103", "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99]\n" ] } ], "source": [ "l = List(list(range(100)))\n", "print(l)" ] }, { "cell_type": "code", "execution_count": 11, "id": "050e6b1b-8062-44f6-9d46-a96356f26a36", "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "[0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99]\n" ] } ], "source": [ "l.delete(1)\n", "print(l)" ] }, { "cell_type": "code", "execution_count": 12, "id": "b95f6f92-0698-4b0d-b899-8f17c3037cef", "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "[2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99]\n" ] } ], "source": [ "l.delete(0)\n", "print(l)" ] }, { "cell_type": "code", "execution_count": 13, "id": "81db57d7-a77b-45ca-ba5f-fc6e0bc1f1d1", "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "[2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98]\n" ] } ], "source": [ "l.delete(99)\n", "print(l)" ] }, { "cell_type": "markdown", "id": "bea293f4-1fbf-4aa7-b938-4804202ab573", "metadata": {}, "source": [ "### Exception handling" ] }, { "cell_type": "markdown", "id": "3af91f18-45fc-4880-857c-16c069f14cdf", "metadata": {}, "source": [ "- Example with `input()`\n", "- Python statement `pass` is a do-nothing placeholder. Cannot omit `except:` block, nor can you have an empty block." ] }, { "cell_type": "markdown", "id": "a5d3ea09-a024-44b7-8cd8-a06ec77ea7e7", "metadata": {}, "source": [ "\n", "\n", "\n", "\n", "\n", "\n", "\n", "\n", "\n", "\n" ] }, { "cell_type": "code", "execution_count": 14, "id": "834ef1e9-fe01-45c6-b023-1983f455372d", "metadata": {}, "outputs": [ { "name": "stdin", "output_type": "stream", "text": [ "Enter a number: asdf\n", "Enter a number: 7.3\n", "Enter a number: -99\n" ] }, { "name": "stdout", "output_type": "stream", "text": [ "-99\n" ] } ], "source": [ "invalid = True\n", "while (invalid):\n", " try:\n", " xstr = input(\"Enter a number: \")\n", " xint = int(xstr)\n", " invalid = False\n", " except:\n", " pass\n", "print(xint)" ] }, { "cell_type": "code", "execution_count": 15, "id": "a1cdf5c3-8698-4e79-95da-15c191112333", "metadata": {}, "outputs": [ { "name": "stdin", "output_type": "stream", "text": [ "Enter a number: asdf\n" ] }, { "name": "stdout", "output_type": "stream", "text": [ "Try again:\n" ] }, { "name": "stdin", "output_type": "stream", "text": [ "Enter a number: 7.3\n" ] }, { "name": "stdout", "output_type": "stream", "text": [ "Try again:\n" ] }, { "name": "stdin", "output_type": "stream", "text": [ "Enter a number: -919\n" ] }, { "name": "stdout", "output_type": "stream", "text": [ "-919\n" ] } ], "source": [ "invalid = True\n", "tryagain = False\n", "while (invalid):\n", " try:\n", " if tryagain:\n", " print(\"Try again:\")\n", " xstr = input(\"Enter a number: \")\n", " xint = int(xstr)\n", " invalid = False\n", " except:\n", " tryagain = True\n", "print(xint)" ] }, { "cell_type": "markdown", "id": "a073f234-181a-47b9-8f39-43a0c259f7a5", "metadata": {}, "source": [ "- Catch a specific type of exception" ] }, { "cell_type": "code", "execution_count": 16, "id": "9a1a0f36-ff84-4533-9e0a-5312cb68a072", "metadata": {}, "outputs": [ { "ename": "ValueError", "evalue": "invalid literal for int() with base 10: 'abc'", "output_type": "error", "traceback": [ "\u001b[31m---------------------------------------------------------------------------\u001b[39m", "\u001b[31mValueError\u001b[39m Traceback (most recent call last)", "\u001b[36mCell\u001b[39m\u001b[36m \u001b[39m\u001b[32mIn[16]\u001b[39m\u001b[32m, line 1\u001b[39m\n\u001b[32m----> \u001b[39m\u001b[32m1\u001b[39m \u001b[38;5;28;43mint\u001b[39;49m\u001b[43m(\u001b[49m\u001b[33;43m\"\u001b[39;49m\u001b[33;43mabc\u001b[39;49m\u001b[33;43m\"\u001b[39;49m\u001b[43m)\u001b[49m\n", "\u001b[31mValueError\u001b[39m: invalid literal for int() with base 10: 'abc'" ] } ], "source": [ "int(\"abc\")" ] }, { "cell_type": "code", "execution_count": 17, "id": "fdaa4a37-5c54-4153-9983-2bd118dd9186", "metadata": {}, "outputs": [ { "name": "stdin", "output_type": "stream", "text": [ "Enter a number: xyz\n", "Enter a number: 748\n" ] }, { "name": "stdout", "output_type": "stream", "text": [ "748\n" ] } ], "source": [ "invalid = True\n", "while (invalid):\n", " try:\n", " xstr = input(\"Enter a number: \")\n", " xint = int(xstr)\n", " invalid = False\n", " except ValueError:\n", " pass\n", "print(xint)" ] }, { "cell_type": "markdown", "id": "9e9e387d-9c2b-44b3-8c32-21a307db12de", "metadata": {}, "source": [ "- Raising an exception in `List()`\n", "- Inserting a negative value raises `ValueError`\n", "- Add negative value to error message" ] }, { "cell_type": "code", "execution_count": 18, "id": "3f7a6da5-1fdd-4553-9d7d-5818d77aef25", "metadata": {}, "outputs": [], "source": [ "class List:\n", " def __init__(self,initlist = []):\n", " self.value = None\n", " self.next = None\n", " for x in initlist:\n", " self.append(x)\n", " return\n", "\n", " def isempty(self):\n", " return(self.value == None)\n", " \n", " def appendi(self,v): # append, iterative\n", " if v < 0:\n", " raise ValueError(\"Negative input: \" + str(v))\n", " if self.isempty():\n", " self.value = v\n", " return\n", " \n", " temp = self\n", " while temp.next != None:\n", " temp = temp.next\n", "\n", " temp.next = List()\n", " temp.next.value = v \n", " return\n", "\n", " def appendr(self,v): # append, recursive\n", " if v < 0:\n", " raise ValueError(\"Negative input: \" + str(v))\n", " if self.isempty():\n", " self.value = v\n", " elif self.next == None:\n", " self.next = List([v])\n", " else:\n", " self.next.appendr(v)\n", " return\n", "\n", " def append(self,v):\n", " self.appendr(v)\n", " return\n", "\n", " def insert(self,v):\n", " if v < 0:\n", " raise ValueError(\"Negative input: \" + str(v))\n", " if self.isempty():\n", " self.value = v\n", " return\n", "\n", " newnode = List()\n", " newnode.value = v\n", " \n", " # Exchange values in self and newnode\n", " (self.value, newnode.value) = (newnode.value, self.value)\n", "\n", " # Switch links\n", " (self.next, newnode.next) = (newnode, self.next)\n", "\n", " return\n", "\n", " def delete(self,v): # delete, recursive\n", " if self.isempty():\n", " return\n", "\n", " if self.value == v:\n", " self.value = None\n", " if self.next != None:\n", " self.value = self.next.value\n", " self.next = self.next.next\n", " return\n", " else:\n", " if self.next != None:\n", " self.next.delete(v)\n", " if self.next.value == None:\n", " self.next = None\n", " return\n", " \n", " def __str__(self):\n", " # Iteratively create a Python list from linked list\n", " # and convert that to a string\n", " selflist = []\n", " if self.isempty():\n", " return(str(selflist))\n", "\n", " temp = self\n", " selflist.append(temp.value)\n", " \n", " while temp.next != None:\n", " temp = temp.next\n", " selflist.append(temp.value)\n", "\n", " return(str(selflist))" ] }, { "cell_type": "code", "execution_count": 19, "id": "064e26ad-9096-48fe-a714-f5396d68a931", "metadata": {}, "outputs": [ { "ename": "ValueError", "evalue": "Negative input: -2", "output_type": "error", "traceback": [ "\u001b[31m---------------------------------------------------------------------------\u001b[39m", "\u001b[31mValueError\u001b[39m Traceback (most recent call last)", "\u001b[36mCell\u001b[39m\u001b[36m \u001b[39m\u001b[32mIn[19]\u001b[39m\u001b[32m, line 1\u001b[39m\n\u001b[32m----> \u001b[39m\u001b[32m1\u001b[39m l = \u001b[43mList\u001b[49m\u001b[43m(\u001b[49m\u001b[43m[\u001b[49m\u001b[32;43m1\u001b[39;49m\u001b[43m,\u001b[49m\u001b[43m-\u001b[49m\u001b[32;43m2\u001b[39;49m\u001b[43m,\u001b[49m\u001b[32;43m3\u001b[39;49m\u001b[43m]\u001b[49m\u001b[43m)\u001b[49m\n\u001b[32m 2\u001b[39m \u001b[38;5;28mprint\u001b[39m(l)\n", "\u001b[36mCell\u001b[39m\u001b[36m \u001b[39m\u001b[32mIn[18]\u001b[39m\u001b[32m, line 6\u001b[39m, in \u001b[36mList.__init__\u001b[39m\u001b[34m(self, initlist)\u001b[39m\n\u001b[32m 4\u001b[39m \u001b[38;5;28mself\u001b[39m.next = \u001b[38;5;28;01mNone\u001b[39;00m\n\u001b[32m 5\u001b[39m \u001b[38;5;28;01mfor\u001b[39;00m x \u001b[38;5;129;01min\u001b[39;00m initlist:\n\u001b[32m----> \u001b[39m\u001b[32m6\u001b[39m \u001b[38;5;28;43mself\u001b[39;49m\u001b[43m.\u001b[49m\u001b[43mappend\u001b[49m\u001b[43m(\u001b[49m\u001b[43mx\u001b[49m\u001b[43m)\u001b[49m\n\u001b[32m 7\u001b[39m \u001b[38;5;28;01mreturn\u001b[39;00m\n", "\u001b[36mCell\u001b[39m\u001b[36m \u001b[39m\u001b[32mIn[18]\u001b[39m\u001b[32m, line 39\u001b[39m, in \u001b[36mList.append\u001b[39m\u001b[34m(self, v)\u001b[39m\n\u001b[32m 38\u001b[39m \u001b[38;5;28;01mdef\u001b[39;00m\u001b[38;5;250m \u001b[39m\u001b[34mappend\u001b[39m(\u001b[38;5;28mself\u001b[39m,v):\n\u001b[32m---> \u001b[39m\u001b[32m39\u001b[39m \u001b[38;5;28;43mself\u001b[39;49m\u001b[43m.\u001b[49m\u001b[43mappendr\u001b[49m\u001b[43m(\u001b[49m\u001b[43mv\u001b[49m\u001b[43m)\u001b[49m\n\u001b[32m 40\u001b[39m \u001b[38;5;28;01mreturn\u001b[39;00m\n", "\u001b[36mCell\u001b[39m\u001b[36m \u001b[39m\u001b[32mIn[18]\u001b[39m\u001b[32m, line 29\u001b[39m, in \u001b[36mList.appendr\u001b[39m\u001b[34m(self, v)\u001b[39m\n\u001b[32m 27\u001b[39m \u001b[38;5;28;01mdef\u001b[39;00m\u001b[38;5;250m \u001b[39m\u001b[34mappendr\u001b[39m(\u001b[38;5;28mself\u001b[39m,v): \u001b[38;5;66;03m# append, recursive\u001b[39;00m\n\u001b[32m 28\u001b[39m \u001b[38;5;28;01mif\u001b[39;00m v < \u001b[32m0\u001b[39m:\n\u001b[32m---> \u001b[39m\u001b[32m29\u001b[39m \u001b[38;5;28;01mraise\u001b[39;00m \u001b[38;5;167;01mValueError\u001b[39;00m(\u001b[33m\"\u001b[39m\u001b[33mNegative input: \u001b[39m\u001b[33m\"\u001b[39m + \u001b[38;5;28mstr\u001b[39m(v))\n\u001b[32m 30\u001b[39m \u001b[38;5;28;01mif\u001b[39;00m \u001b[38;5;28mself\u001b[39m.isempty():\n\u001b[32m 31\u001b[39m \u001b[38;5;28mself\u001b[39m.value = v\n", "\u001b[31mValueError\u001b[39m: Negative input: -2" ] } ], "source": [ "l = List([1,-2,3])\n", "print(l)" ] }, { "cell_type": "code", "execution_count": 20, "id": "52e5eaee-4e79-4131-969a-08dae15cb361", "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "oops\n" ] } ], "source": [ "try:\n", " l = List([1,-2,3])\n", "except ValueError:\n", " print(\"oops\")" ] }, { "cell_type": "code", "execution_count": 21, "id": "c4144ec9-e7d5-430c-b9ca-5571d50095a3", "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "Negative input: -2\n" ] } ], "source": [ "try:\n", " l = List([1,-2,3])\n", "except ValueError as errormsg: # Saves error value in errormsg\n", " print(errormsg)" ] } ], "metadata": { "kernelspec": { "display_name": "Python 3 (ipykernel)", "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": "3.13.5" } }, "nbformat": 4, "nbformat_minor": 5 }