{ "cells": [ { "cell_type": "markdown", "id": "12b02b53", "metadata": {}, "source": [ "

Lists, Tuples and Loops

\n", "
\n", "

Lists

\n", "
Lists are a great tool for organising all kind of info. In contrast to most other languages one can mix types\n", "

Initialise and index

" ] }, { "cell_type": "code", "execution_count": 26, "id": "c913485b", "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "L1: [1, 5, 'five', [1, 2, 3], 0]\n", "L2: ['Hey', 4.2, False, [1, 5, 'five', [1, 2, 3], 0]]\n", "The second letter of the third object in the fourth object in L2: i\n", "The object 1 step back from the end in L2: False\n", "Element 1 to 3(not included) [4.2, False, [1, 5, 'five', [1, 2, 3], 0]]\n", "All elements jumping 2 steps [1, 'five', 0]\n" ] } ], "source": [ "#Basic lists\n", "l1 = [1,5,\"five\",[1,2,3],True]\n", "l2 = [\"Hey\",4.2,False,l1]\n", "\n", "#Changing content (list are mutable objects)\n", "l1[4] = 0\n", "print(f\"L1: {l1}\")\n", "print(f\"L2: {l2}\")\n", "#Digging deep\n", "print(f\"The second letter of the third object in the fourth object in L2: {l2[3][2][1]}\")\n", "#Negative index\n", "print(f\"The object 1 step back from the end in L2: {l2[-2]}\")\n", "\n", "#Getting pieces of a list(slicing) - works the same as with strings, just give the range we want [start:stop].\n", "#Note that object at \"start\" is included, but not the object at \"stop\"\n", "print(f\"Element 1 to 3(not included) {l2[1:3]}\")\n", "#Picking with a stride using [startindex:stop-place:stride]\n", "print(f\"All elements jumping 2 steps {l1[::2]}\")" ] }, { "cell_type": "markdown", "id": "1fa8e0d6", "metadata": {}, "source": [ "

List methods

\n", "\n", "
\n", "Lets try som of these" ] }, { "cell_type": "code", "execution_count": 27, "id": "12162899", "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "Apples: 2\n", "Tangerines: 0\n", "Next banana, counting from pos: 3\n", "Reversed fruits: ['banana', 'apple', 'kiwi', 'banana', 'pear', 'apple', 'orange']\n", "Longer list: ['banana', 'apple', 'kiwi', 'banana', 'pear', 'apple', 'orange', 'grape']\n", "Original list now sorted: ['apple', 'apple', 'banana', 'banana', 'grape', 'kiwi', 'orange', 'pear']\n", "Popped fruit: pear\n", "The list after popping: ['apple', 'apple', 'banana', 'banana', 'grape', 'kiwi', 'orange']\n" ] } ], "source": [ "fruits = ['orange', 'apple', 'pear', 'banana', 'kiwi', 'apple', 'banana']\n", "#How many of the fruits\n", "print(f\"Apples: {fruits.count('apple')}\")\n", "print(f\"Tangerines: {fruits.count('tangerine')}\")\n", "#Finding position for the first banana\n", "pos = fruits.index('banana')\n", "#Find next banana starting at that position\n", "print(f\"Next banana, counting from pos: {fruits.index('banana', pos)}\") \n", "\n", "fruits.reverse()\n", "print(f\"Reversed fruits: {fruits}\")\n", "\n", "#Add element\n", "fruits.append('grape')\n", "print(f\"Longer list: {fruits}\")\n", "\n", "#This will sort list in place\n", "fruits.sort()\n", "print(f\"Original list now sorted: {fruits}\")\n", "#Lifting out the last element actually removing it and returning it as output\n", "print(f\"Popped fruit: {fruits.pop()}\")\n", "print(f\"The list after popping: {fruits}\")" ] }, { "cell_type": "markdown", "id": "08575031", "metadata": {}, "source": [ "

Tuples - Immutable lists

\n", "There is a special kind of \"list\". It's caled Tuple
\n", "Lets try this.." ] }, { "cell_type": "code", "execution_count": 28, "id": "07b46975", "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "New list: ((12345, 54321, 'hello!'), (1, 2, 3, 4, 5))\n", "Our tuple v: ([1, 2, 3], [3, 2, 1])\n", "Our tuple new: ([10, 2, 3], [3, 2, 1])\n", "v now as a list: [[10, 2, 3], [3, 2, 1]]\n", "a = 2, b = 1\n" ] } ], "source": [ "#Basic tuple\n", "t = 12345, 54321, 'hello!'\n", "#Getting an element, exactly as with lists\n", "t[0]\n", "\n", "# Tuples may be nested:\n", "u = t, (1, 2, 3, 4, 5)\n", "print(f\"New list: {u}\")\n", "\n", "# Tuples are immutable:\n", "#t[0] = 88888, wont work\n", "\n", "# but they can contain mutable objects:\n", "v = ([1, 2, 3], [3, 2, 1])\n", "print(f\"Our tuple v: {v}\")\n", "new = v\n", "new[0][0] = 10\n", "print(f\"Our tuple new: {new}\")\n", "#One can transform a Tuple into a list quite easily\n", "myList = list(v)\n", "print(f\"v now as a list: {myList}\")\n", "\n", "#Clever use of tuples, swapping places/values.\n", "a = 1\n", "b = 2\n", "b,a = a,b\n", "print(f\"a = {a}, b = {b}\")\n" ] }, { "cell_type": "markdown", "id": "5cb130fc", "metadata": {}, "source": [ "

Loops

\n", "

We need to repeat things quite often. There are 2 main types of loops

\n", "" ] }, { "cell_type": "code", "execution_count": 3, "id": "63db02ef", "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "Lap nr: 0\n", "Lap nr: 1\n", "Lap nr: 2\n", "Lap nr: 3\n", "Lap nr: 4\n", "End of while-loop\n" ] } ], "source": [ "#Basic while loop\n", "i = 0\n", "while i < 5:\n", " print(f\"Lap nr: {i}\")\n", " i += 1\n", "else:\n", " print(\"End of while-loop\")\n" ] }, { "cell_type": "markdown", "id": "f644ba17", "metadata": {}, "source": [ "

Sometimes we need to check user input and give the user a chance to give som decent input

" ] }, { "cell_type": "code", "execution_count": 29, "id": "297b1036", "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "Yiihaaa\n", "Yiihaaa\n", "Yiihaaa\n" ] } ], "source": [ "def main():\n", " number = get_number()\n", " scream(number)\n", "\n", "#Getting input, handling the fact that you can get bad input\n", "def get_number():\n", " while True:\n", " n = int(input(\"How many times shall I scream? \"))\n", " if n > 0:\n", " break\n", " return n\n", "\n", "\n", "def scream(n):\n", " for _ in range(n):\n", " print(\"Yiihaaa\")\n", "\n", "main()" ] }, { "cell_type": "code", "execution_count": 31, "id": "83a038a1", "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "Lap nr: 0\n", "Lap nr: 1\n", "Lap nr: 2\n", "Lap nr: 3\n", "Lap nr: 4\n", "Skipping Lap nr: 1\n", "Skipping Lap nr: 3\n", "Skipping Lap nr: 5\n", "Skipping Lap nr: 7\n", "Skipping Lap nr: 9\n", "This will be repated \n", "This will be repated \n", "This will be repated \n", "This will be repated \n", "This will be repated \n", "\n" ] } ], "source": [ "#Basic for-loop\n", "for i in range(5):\n", " print(f\"Lap nr: {i}\")\n", "#With limits and stride\n", "for i in range(1,10,2):\n", " print(f\"Skipping Lap nr: {i}\")\n", "\n", "#Fun fact with print...\n", "print(\"This will be repated \\n\"*5)\n" ] }, { "cell_type": "markdown", "id": "efadec28", "metadata": {}, "source": [ "

A really nice thing with for-loops and lists are that we can loop through lists. The fact is that when we use range we create a kind of a tuple on the fly to loop through.

\n", "Lets try this" ] }, { "cell_type": "code", "execution_count": 5, "id": "78ddaa07", "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "cat 3\n", "window 6\n", "defenestrate 12\n" ] } ], "source": [ "# Measure some strings:\n", "words = ['cat', 'window', 'defenestrate']\n", "for w in words:\n", " print(w, len(w))" ] }, { "cell_type": "markdown", "id": "9397df8d", "metadata": {}, "source": [ "Lets try something a bit more mathematical, Fibonacci ;)" ] }, { "cell_type": "code", "execution_count": 35, "id": "a8173100", "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "[2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181, 6765, 10946, 17711, 28657, 46368, 75025, 121393, 196418, 317811, 514229, 832040, 1346269, 2178309, 3524578]\n" ] } ], "source": [ "# Calculates and stores the first n Fibonacci numbers\n", "n = int(input(\"How high? \"))\n", "#The first 2\n", "fib = [2, 3]\n", "#Crunching through the algorithm creating a list\n", "for i in range(2, n+1):\n", " fib.append(fib[i-1] + fib[i-2])\n", "print(fib)" ] }, { "cell_type": "code", "execution_count": 36, "id": "e79bcdc8", "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181 6765 10946 17711 28657 46368 75025 121393 196418 317811 514229 832040 1346269" ] } ], "source": [ "# Calculates the first n Fibonacci numbers without storing\n", "n = int(input(\"How high? \"))\n", "# Keep track of the two most recent Fibonacci numbers\n", "a, b = 1, 1\n", "print(a, b, end='')\n", "for i in range(2, n+1):\n", " # The next number (b) is a+b, and a becomes the previous b, using tuple swap\n", " a, b = b, a+b\n", " print(' ', b, end='')" ] }, { "cell_type": "markdown", "id": "56794cf4", "metadata": {}, "source": [ "

break and continue in loops

\n", "

This is really useful

\n", "