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dict tutorials
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‎ngs-61-intro-to-dicts.ipynb

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{
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"metadata": {
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"name": "ngs-61-intro-to-dicts"
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},
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"nbformat": 3,
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"worksheets": [
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{
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"cells": [
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{
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"cell_type": "markdown",
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"source": [
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"Goal: take some data from counting birds, and ask questions of it.",
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"",
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"In particular, how many birds did we see of each type?"
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]
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},
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{
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"cell_type": "code",
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"input": [
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"s = \"\"\"",
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"bluejay",
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"goldfinch",
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"goldfinch",
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"bald eagle",
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"ostrich",
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"bluejay",
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"goose",
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"goose",
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"goose",
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"goose",
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"goose",
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"goose",
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"goose",
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"duck",
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"\"\"\""
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],
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"language": "python",
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"outputs": [],
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"prompt_number": 1
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},
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{
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"cell_type": "markdown",
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"source": [
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"First, let's transform this text list into a \"real\" python list."
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]
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},
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{
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"cell_type": "code",
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"input": [
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"birdlist = s.split('\\n')",
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"birdlist = [ x for x in birdlist if x ]",
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"birdlist"
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],
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"language": "python",
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"outputs": [
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{
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"output_type": "pyout",
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"prompt_number": 6,
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"text": [
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"['bluejay',",
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" 'goldfinch',",
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" 'goldfinch',",
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" 'bald eagle',",
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" 'ostrich',",
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" 'bluejay',",
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" 'goose',",
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" 'goose',",
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" 'goose',",
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" 'goose',",
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" 'goose',",
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" 'goose',",
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" 'goose',",
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" 'duck']"
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]
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}
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],
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"prompt_number": 6
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},
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{
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"cell_type": "code",
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"input": [
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"countlist = []",
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"for bird in birdlist:",
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" newcountlist = []",
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" found = False",
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" for (j, count) in countlist:",
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" if j == bird:",
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" found = True",
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" count += 1",
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" newcountlist.append((j, count))",
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" if not found:",
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" newcountlist.append((bird, 1))",
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" countlist = newcountlist",
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" ",
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"countlist"
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],
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"language": "python",
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"outputs": [
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{
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"output_type": "pyout",
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"prompt_number": 9,
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"text": [
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"[('bluejay', 2),",
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" ('goldfinch', 2),",
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" ('bald eagle', 1),",
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" ('ostrich', 1),",
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" ('goose', 7),",
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" ('duck', 1)]"
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]
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}
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],
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"prompt_number": 9
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},
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{
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"cell_type": "markdown",
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"source": [
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"Let's use a dictionary instead"
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]
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},
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{
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"cell_type": "code",
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"input": [
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"birddict = {}",
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"# set the value associated with the key 'goose' to the number 7",
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"birddict['goose'] = 7",
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"# get the value associated with the key 'goose'",
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"print birddict['goose']"
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],
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"language": "python",
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"outputs": [
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{
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"output_type": "stream",
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"stream": "stdout",
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"text": [
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"7",
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""
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]
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}
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],
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"prompt_number": 10
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},
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{
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"cell_type": "code",
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"input": [
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"birddict = {}",
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"for bird in birdlist:",
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" birddict[bird] = 0",
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" ",
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"for bird in birdlist:",
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" birddict[bird] = birddict[bird] + 1",
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"",
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"birddict"
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],
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"language": "python",
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"outputs": [
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{
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"output_type": "pyout",
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"prompt_number": 14,
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"text": [
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"{'bald eagle': 1,",
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" 'bluejay': 2,",
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" 'duck': 1,",
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" 'goldfinch': 2,",
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" 'goose': 7,",
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" 'ostrich': 1}"
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]
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}
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],
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"prompt_number": 14
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},
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{
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"cell_type": "code",
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"input": [
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"birddict = {}",
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"",
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"for bird in birdlist:",
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" if bird not in birddict:",
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" birddict[bird] = 1",
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" else:",
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" birddict[bird] = birddict[bird] + 1",
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"",
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"birddict"
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],
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"language": "python",
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"outputs": [
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{
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"output_type": "pyout",
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"prompt_number": 17,
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"text": [
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"{'bald eagle': 1,",
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" 'bluejay': 2,",
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" 'duck': 1,",
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" 'goldfinch': 2,",
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" 'goose': 7,",
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" 'ostrich': 1}"
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]
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}
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],
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"prompt_number": 17
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},
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{
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"cell_type": "code",
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"input": [
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"birddict = {}",
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"",
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"for bird in birdlist:",
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" birddict[bird] = birddict.get(bird, 0) + 1",
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"",
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"birddict"
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],
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"language": "python",
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"outputs": [
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{
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"output_type": "pyout",
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"prompt_number": 18,
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"text": [
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"{'bald eagle': 1,",
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" 'bluejay': 2,",
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" 'duck': 1,",
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" 'goldfinch': 2,",
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" 'goose': 7,",
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" 'ostrich': 1}"
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]
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}
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],
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"prompt_number": 18
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},
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{
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"cell_type": "code",
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"input": [
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"birddict.keys()"
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],
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"language": "python",
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"outputs": [
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{
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"output_type": "pyout",
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"prompt_number": 19,
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"text": [
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"['bald eagle', 'bluejay', 'ostrich', 'goose', 'goldfinch', 'duck']"
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]
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}
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],
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"prompt_number": 19
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},
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{
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"cell_type": "code",
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"input": [
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"birddict.values()"
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],
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"language": "python",
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"outputs": [
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{
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"output_type": "pyout",
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"prompt_number": 20,
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"text": [
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"[1, 2, 1, 7, 2, 1]"
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]
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}
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],
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"prompt_number": 20
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},
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{
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"cell_type": "code",
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"input": [
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"birddict.items()"
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],
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"language": "python",
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"outputs": [
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{
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"output_type": "pyout",
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"prompt_number": 21,
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"text": [
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"[('bald eagle', 1),",
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" ('bluejay', 2),",
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" ('ostrich', 1),",
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" ('goose', 7),",
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" ('goldfinch', 2),",
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" ('duck', 1)]"
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]
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}
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],
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"prompt_number": 21
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},
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{
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"cell_type": "code",
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"input": [
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"x = sorted(birddict.items())",
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"x"
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],
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"language": "python",
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"outputs": [
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{
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"output_type": "pyout",
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"prompt_number": 23,
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"text": [
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"[('bald eagle', 1),",
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" ('bluejay', 2),",
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" ('duck', 1),",
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" ('goldfinch', 2),",
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" ('goose', 7),",
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" ('ostrich', 1)]"
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]
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}
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],
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"prompt_number": 23
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},
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{
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"cell_type": "code",
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"input": [
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"def get_count(a):",
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" return a[1]",
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"",
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"# Sort by count, not by bird name; use get_count to get the count.",
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"x = sorted(birddict.items(), key=get_count)",
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"# by default sorted goes from least to most; reverse that.",
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"x.reverse()",
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"x"
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],
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"language": "python",
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"outputs": [
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{
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"output_type": "pyout",
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"prompt_number": 33,
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"text": [
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"[('goose', 7),",
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" ('goldfinch', 2),",
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" ('bluejay', 2),",
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" ('duck', 1),",
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" ('ostrich', 1),",
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" ('bald eagle', 1)]"
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]
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}
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],
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"prompt_number": 33
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},
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{
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"cell_type": "code",
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"input": [
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""
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],
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"language": "python",
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"outputs": []
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},
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{
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"cell_type": "code",
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"input": [
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""
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],
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"language": "python",
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"outputs": []
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}
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]
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}
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]
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}

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