book

Python Crash Course, 3rd Edition

by Eric Matthes

January 2023

Intermediate to advanced

552 pages

13h 38m

English

No Starch Press

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Who Is This Book For?What Can You Expect to Learn?Online ResourcesWhy Python?
Setting Up Your Programming EnvironmentPython VersionsRunning Snippets of Python CodeAbout the VS Code EditorPython on Different Operating SystemsPython on WindowsPython on macOSPython on LinuxRunning a Hello World ProgramInstalling the Python Extension for VS CodeRunning hello_world.pyTroubleshootingRunning Python Programs from a TerminalOn WindowsOn macOS and LinuxExercise 1-1: python.orgExercise 1-2: Hello World TyposExercise 1-3: Infinite SkillsSummary

What Really Happens When You Run hello_world.pyVariablesNaming and Using VariablesAvoiding Name Errors When Using VariablesVariables Are LabelsExercise 2-1: Simple MessageExercise 2-2: Simple MessagesStringsChanging Case in a String with MethodsUsing Variables in StringsAdding Whitespace to Strings with Tabs or NewlinesStripping WhitespaceRemoving PrefixesAvoiding Syntax Errors with StringsExercise 2-3: Personal MessageExercise 2-4: Name CasesExercise 2-5: Famous QuoteExercise 2-6: Famous Quote 2Exercise 2-7: Stripping NamesExercise 2-8: File ExtensionsNumbersIntegersFloatsIntegers and FloatsUnderscores in NumbersMultiple AssignmentConstantsExercise 2-9: Number EightExercise 2-10: Favorite NumberCommentsHow Do You Write Comments?What Kinds of Comments Should You Write?Exercise 2-11: Adding CommentsThe Zen of PythonExercise 2-12: Zen of PythonSummary
What Is a List?Accessing Elements in a ListIndex Positions Start at 0, Not 1Using Individual Values from a ListExercise 3-1: NamesExercise 3-2: GreetingsExercise 3-3: Your Own ListModifying, Adding, and Removing ElementsModifying Elements in a ListAdding Elements to a ListRemoving Elements from a ListExercise 3-4: Guest ListExercise 3-5: Changing Guest ListExercise 3-6: More GuestsExercise 3-7: Shrinking Guest ListOrganizing a ListSorting a List Permanently with the sort() MethodSorting a List Temporarily with the sorted() FunctionPrinting a List in Reverse OrderFinding the Length of a ListExercise 3-8: Seeing the WorldExercise 3-9: Dinner GuestsExercise 3-10: Every FunctionAvoiding Index Errors When Working with ListsExercise 3-11: Intentional ErrorSummary
Looping Through an Entire ListA Closer Look at LoopingDoing More Work Within a for LoopDoing Something After a for LoopAvoiding Indentation ErrorsForgetting to IndentForgetting to Indent Additional LinesIndenting UnnecessarilyIndenting Unnecessarily After the LoopForgetting the ColonExercise 4-1: PizzasExercise 4-2: AnimalsMaking Numerical ListsUsing the range() FunctionUsing range() to Make a List of NumbersSimple Statistics with a List of NumbersList ComprehensionsExercise 4-3: Counting to TwentyExercise 4-4: One MillionExercise 4-5: Summing a MillionExercise 4-6: Odd NumbersExercise 4-7: ThreesExercise 4-8: CubesExercise 4-9: Cube ComprehensionWorking with Part of a ListSlicing a ListLooping Through a SliceCopying a ListExercise 4-10: SlicesExercise 4-11: My Pizzas, Your PizzasExercise 4-12: More LoopsTuplesDefining a TupleLooping Through All Values in a TupleWriting Over a TupleExercise 4-13: BuffetStyling Your CodeThe Style GuideIndentationLine LengthBlank LinesOther Style GuidelinesExercise 4-14: PEP 8Exercise 4-15: Code ReviewSummary
A Simple ExampleConditional TestsChecking for EqualityIgnoring Case When Checking for EqualityChecking for InequalityNumerical ComparisonsChecking Multiple ConditionsChecking Whether a Value Is in a ListChecking Whether a Value Is Not in a ListBoolean ExpressionsExercise 5-1: Conditional TestsExercise 5-2: More Conditional Testsif StatementsSimple if Statementsif-else StatementsThe if-elif-else ChainUsing Multiple elif BlocksOmitting the else BlockTesting Multiple ConditionsExercise 5-3: Alien Colors #1Exercise 5-4: Alien Colors #2Exercise 5-5: Alien Colors #3Exercise 5-6: Stages of LifeExercise 5-7: Favorite FruitUsing if Statements with ListsChecking for Special ItemsChecking That a List Is Not EmptyUsing Multiple ListsExercise 5-8: Hello AdminExercise 5-9: No UsersExercise 5-10: Checking UsernamesExercise 5-11: Ordinal NumbersStyling Your if StatementsExercise 5-12: Styling if StatementsExercise 5-13: Your IdeasSummary
A Simple DictionaryWorking with DictionariesAccessing Values in a DictionaryAdding New Key-Value PairsStarting with an Empty DictionaryModifying Values in a DictionaryRemoving Key-Value PairsA Dictionary of Similar ObjectsUsing get() to Access ValuesExercise 6-1: PersonExercise 6-2: Favorite NumbersExercise 6-3: GlossaryLooping Through a DictionaryLooping Through All Key-Value PairsLooping Through All the Keys in a DictionaryLooping Through a Dictionary’s Keys in a Particular OrderLooping Through All Values in a DictionaryExercise 6-4: Glossary 2Exercise 6-5: RiversExercise 6-6: PollingNestingA List of DictionariesA List in a DictionaryA Dictionary in a DictionaryExercise 6-7: PeopleExercise 6-8: PetsExercise 6-9: Favorite PlacesExercise 6-10: Favorite NumbersExercise 6-11: CitiesExercise 6-12: ExtensionsSummary
How the input() Function WorksWriting Clear PromptsUsing int() to Accept Numerical InputThe Modulo OperatorExercise 7-1: Rental CarExercise 7-2: Restaurant SeatingExercise 7-3: Multiples of TenIntroducing while LoopsThe while Loop in ActionLetting the User Choose When to QuitUsing a FlagUsing break to Exit a LoopUsing continue in a LoopAvoiding Infinite LoopsExercise 7-4: Pizza ToppingsExercise 7-5: Movie TicketsExercise 7-6: Three ExitsExercise 7-7: InfinityUsing a while Loop with Lists and DictionariesMoving Items from One List to AnotherRemoving All Instances of Specific Values from a ListFilling a Dictionary with User InputExercise 7-8: DeliExercise 7-9: No PastramiExercise 7-10: Dream VacationSummary
Defining a FunctionPassing Information to a FunctionArguments and ParametersExercise 8-1: MessageExercise 8-2: Favorite BookPassing ArgumentsPositional ArgumentsKeyword ArgumentsDefault ValuesEquivalent Function CallsAvoiding Argument ErrorsExercise 8-3: T-ShirtExercise 8-4: Large ShirtsExercise 8-5: CitiesReturn ValuesReturning a Simple ValueMaking an Argument OptionalReturning a DictionaryUsing a Function with a while LoopExercise 8-6: City NamesExercise 8-7: AlbumExercise 8-8: User AlbumsPassing a ListModifying a List in a FunctionPreventing a Function from Modifying a ListExercise 8-9: MessagesExercise 8-10: Sending MessagesExercise 8-11: Archived MessagesPassing an Arbitrary Number of ArgumentsMixing Positional and Arbitrary ArgumentsUsing Arbitrary Keyword ArgumentsExercise 8-12: SandwichesExercise 8-13: User ProfileExercise 8-14: CarsStoring Your Functions in ModulesImporting an Entire ModuleImporting Specific FunctionsUsing as to Give a Function an AliasUsing as to Give a Module an AliasImporting All Functions in a ModuleStyling FunctionsExercise 8-15: Printing ModelsExercise 8-16: ImportsExercise 8-17: Styling FunctionsSummary
Creating and Using a ClassCreating the Dog ClassThe __init__() MethodMaking an Instance from a ClassExercise 9-1: RestaurantExercise 9-2: Three RestaurantsExercise 9-3: UsersWorking with Classes and InstancesThe Car ClassSetting a Default Value for an AttributeModifying Attribute ValuesExercise 9-4: Number ServedExercise 9-5: Login AttemptsInheritanceThe __init__() Method for a Child ClassDefining Attributes and Methods for the Child ClassOverriding Methods from the Parent ClassInstances as AttributesModeling Real-World ObjectsExercise 9-6: Ice Cream StandExercise 9-7: AdminExercise 9-8: PrivilegesExercise 9-9: Battery UpgradeImporting ClassesImporting a Single ClassStoring Multiple Classes in a ModuleImporting Multiple Classes from a ModuleImporting an Entire ModuleImporting All Classes from a ModuleImporting a Module into a ModuleUsing AliasesFinding Your Own WorkflowExercise 9-10: Imported RestaurantExercise 9-11: Imported AdminExercise 9-12: Multiple ModulesThe Python Standard LibraryExercise 9-13: DiceExercise 9-14: LotteryExercise 9-15: Lottery AnalysisExercise 9-16: Python Module of the WeekStyling ClassesSummary
Reading from a FileReading the Contents of a FileRelative and Absolute File PathsAccessing a File’s LinesWorking with a File’s ContentsLarge Files: One Million DigitsIs Your Birthday Contained in Pi?Exercise 10-1: Learning PythonExercise 10-2: Learning CExercise 10-3: Simpler CodeWriting to a FileWriting a Single LineWriting Multiple LinesExercise 10-4: GuestExercise 10-5: Guest BookExceptionsHandling the ZeroDivisionError ExceptionUsing try-except BlocksUsing Exceptions to Prevent CrashesThe else BlockHandling the FileNotFoundError ExceptionAnalyzing TextWorking with Multiple FilesFailing SilentlyDeciding Which Errors to ReportExercise 10-6: AdditionExercise 10-7: Addition CalculatorExercise 10-8: Cats and DogsExercise 10-9: Silent Cats and DogsExercise 10-10: Common WordsStoring DataUsing json.dumps() and json.loads()Saving and Reading User-Generated DataRefactoringExercise 10-11: Favorite NumberExercise 10-12: Favorite Number RememberedExercise 10-13: User DictionaryExercise 10-14: Verify UserSummary
Installing pytest with pipUpdating pipInstalling pytestTesting a FunctionUnit Tests and Test CasesA Passing TestRunning a TestA Failing TestResponding to a Failed TestAdding New TestsExercise 11-1: City, CountryExercise 11-2: PopulationTesting a ClassA Variety of AssertionsA Class to TestTesting the AnonymousSurvey ClassUsing FixturesExercise 11-3: EmployeeSummary
Planning Your ProjectInstalling PygameStarting the Game ProjectCreating a Pygame Window and Responding to User InputControlling the Frame RateSetting the Background ColorCreating a Settings ClassAdding the Ship ImageCreating the Ship ClassDrawing the Ship to the ScreenRefactoring: The _check_events() and _update_screen() MethodsThe _check_events() MethodThe _update_screen() MethodExercise 12-1: Blue SkyExercise 12-2: Game CharacterPiloting the ShipResponding to a KeypressAllowing Continuous MovementMoving Both Left and RightAdjusting the Ship’s SpeedLimiting the Ship’s RangeRefactoring _check_events()Pressing Q to QuitRunning the Game in Fullscreen ModeA Quick Recapalien_invasion.pysettings.pyship.pyExercise 12-3: Pygame DocumentationExercise 12-4: RocketExercise 12-5: KeysShooting BulletsAdding the Bullet SettingsCreating the Bullet ClassStoring Bullets in a GroupFiring BulletsDeleting Old BulletsLimiting the Number of BulletsCreating the _update_bullets() MethodExercise 12-6: Sideways ShooterSummary
Reviewing the ProjectCreating the First AlienCreating the Alien ClassCreating an Instance of the AlienBuilding the Alien FleetCreating a Row of AliensRefactoring _create_fleet()Adding RowsExercise 13-1: StarsExercise 13-2: Better StarsMaking the Fleet MoveMoving the Aliens RightCreating Settings for Fleet DirectionChecking Whether an Alien Has Hit the EdgeDropping the Fleet and Changing DirectionExercise 13-3: RaindropsExercise 13-4: Steady RainShooting AliensDetecting Bullet CollisionsMaking Larger Bullets for TestingRepopulating the FleetSpeeding Up the BulletsRefactoring _update_bullets()Exercise 13-5: Sideways Shooter Part 2Ending the GameDetecting Alien-Ship CollisionsResponding to Alien-Ship CollisionsAliens That Reach the Bottom of the ScreenGame Over!Identifying When Parts of the Game Should RunExercise 13-6: Game OverSummary
Adding the Play ButtonCreating a Button ClassDrawing the Button to the ScreenStarting the GameResetting the GameDeactivating the Play ButtonHiding the Mouse CursorExercise 14-1: Press P to PlayExercise 14-2: Target PracticeLeveling UpModifying the Speed SettingsResetting the SpeedExercise 14-3: Challenging Target PracticeExercise 14-4: Difficulty LevelsScoringDisplaying the ScoreMaking a ScoreboardUpdating the Score as Aliens Are Shot DownResetting the ScoreMaking Sure to Score All HitsIncreasing Point ValuesRounding the ScoreHigh ScoresDisplaying the LevelDisplaying the Number of ShipsExercise 14-5: All-Time High ScoreExercise 14-6: RefactoringExercise 14-7: Expanding the GameExercise 14-8: Sideways Shooter, Final VersionSummary
Installing MatplotlibPlotting a Simple Line GraphChanging the Label Type and Line ThicknessCorrecting the PlotUsing Built-in StylesPlotting and Styling Individual Points with scatter()Plotting a Series of Points with scatter()Calculating Data AutomaticallyCustomizing Tick LabelsDefining Custom ColorsUsing a ColormapSaving Your Plots AutomaticallyExercise 15-1: CubesExercise 15-2: Colored CubesRandom WalksCreating the RandomWalk ClassChoosing DirectionsPlotting the Random WalkGenerating Multiple Random WalksStyling the WalkExercise 15-3: Molecular MotionExercise 15-4: Modified Random WalksExercise 15-5: RefactoringRolling Dice with PlotlyInstalling PlotlyCreating the Die ClassRolling the DieAnalyzing the ResultsMaking a HistogramCustomizing the PlotRolling Two DiceFurther CustomizationsRolling Dice of Different SizesSaving FiguresExercise 15-6: Two D8sExercise 15-7: Three DiceExercise 15-8: MultiplicationExercise 15-9: Die ComprehensionsExercise 15-10: Practicing with Both LibrariesSummary
The CSV File FormatParsing the CSV File HeadersPrinting the Headers and Their PositionsExtracting and Reading DataPlotting Data in a Temperature ChartThe datetime ModulePlotting DatesPlotting a Longer TimeframePlotting a Second Data SeriesShading an Area in the ChartError CheckingDownloading Your Own DataExercise 16-1: Sitka RainfallExercise 16-2: Sitka–Death Valley ComparisonExercise 16-3: San FranciscoExercise 16-4: Automatic IndexesExercise 16-5: ExploreMapping Global Datasets: GeoJSON FormatDownloading Earthquake DataExamining GeoJSON DataMaking a List of All EarthquakesExtracting MagnitudesExtracting Location DataBuilding a World MapRepresenting MagnitudesCustomizing Marker ColorsOther Color ScalesAdding Hover TextExercise 16-6: RefactoringExercise 16-7: Automated TitleExercise 16-8: Recent EarthquakesExercise 16-9: World FiresSummary
Using an APIGit and GitHubRequesting Data Using an API CallInstalling RequestsProcessing an API ResponseWorking with the Response DictionarySummarizing the Top RepositoriesMonitoring API Rate LimitsVisualizing Repositories Using PlotlyStyling the ChartAdding Custom TooltipsAdding Clickable LinksCustomizing Marker ColorsMore About Plotly and the GitHub APIThe Hacker News APIExercise 17-1: Other LanguagesExercise 17-2: Active DiscussionsExercise 17-3: Testing python_repos.pyExercise 17-4: Further ExplorationSummary
Setting Up a ProjectWriting a SpecCreating a Virtual EnvironmentActivating the Virtual EnvironmentInstalling DjangoCreating a Project in DjangoCreating the DatabaseViewing the ProjectExercise 18-1: New ProjectsStarting an AppDefining ModelsActivating ModelsThe Django Admin SiteDefining the Entry ModelMigrating the Entry ModelRegistering Entry with the Admin SiteThe Django ShellExercise 18-2: Short EntriesExercise 18-3: The Django APIExercise 18-4: PizzeriaMaking Pages: The Learning Log Home PageMapping a URLWriting a ViewWriting a TemplateExercise 18-5: Meal PlannerExercise 18-6: Pizzeria Home PageBuilding Additional PagesTemplate InheritanceThe Topics PageIndividual Topic PagesExercise 18-7: Template DocumentationExercise 18-8: Pizzeria PagesSummary
Allowing Users to Enter DataAdding New TopicsAdding New EntriesEditing EntriesExercise 19-1: BlogSetting Up User AccountsThe accounts AppThe Login PageLogging OutThe Registration PageExercise 19-2: Blog AccountsAllowing Users to Own Their DataRestricting Access with @login_requiredConnecting Data to Certain UsersRestricting Topics Access to Appropriate UsersProtecting a User’s TopicsProtecting the edit_entry PageAssociating New Topics with the Current UserExercise 19-3: RefactoringExercise 19-4: Protecting new_entryExercise 19-5: Protected BlogSummary
Styling Learning LogThe django-bootstrap5 AppUsing Bootstrap to Style Learning LogModifying base.htmlStyling the Home Page Using a JumbotronStyling the Login PageStyling the Topics PageStyling the Entries on the Topic PageExercise 20-1: Other FormsExercise 20-2: Stylish BlogDeploying Learning LogMaking a Platform.sh AccountInstalling the Platform.sh CLIInstalling platformshconfigCreating a requirements.txt FileAdditional Deployment RequirementsAdding Configuration FilesModifying settings.py for Platform.shUsing Git to Track the Project’s FilesCreating a Project on Platform.shPushing to Platform.shViewing the Live ProjectRefining the Platform.sh DeploymentCreating Custom Error PagesOngoing DevelopmentDeleting a Project on Platform.shExercise 20-3: Live BlogExercise 20-4: Extended Learning LogSummary
Python on WindowsUsing py Instead of pythonRerunning the InstallerPython on macOSAccidentally Installing Apple’s Version of PythonPython 2 on Older Versions of macOSPython on LinuxUsing the Default Python InstallationInstalling the Latest Version of PythonChecking Which Version of Python You’re UsingPython Keywords and Built-in FunctionsPython KeywordsPython Built-in Functions
Working Efficiently with VS CodeConfiguring VS CodeVS Code ShortcutsOther Text Editors and IDEsIDLEGeanySublime TextEmacs and VimPyCharmJupyter Notebooks
First StepsTry It AgainTake a BreakRefer to This Book’s ResourcesSearching OnlineStack OverflowThe Official Python DocumentationOfficial Library Documentationr/learnpythonBlog PostsDiscordSlack
Installing GitConfiguring GitMaking a ProjectIgnoring FilesInitializing a RepositoryChecking the StatusAdding Files to the RepositoryMaking a CommitChecking the LogThe Second CommitAbandoning ChangesChecking Out Previous CommitsDeleting the Repository
Understanding DeploymentsBasic TroubleshootingFollow Onscreen SuggestionsRead the Log OutputOS-Specific TroubleshootingDeploying from WindowsDeploying from macOSDeploying from LinuxOther Deployment Approaches

Content preview from Python Crash Course, 3rd Edition

18 Getting Started with Django

As the internet has evolved, the line between websites and mobile apps has blurred. Websites and apps both help users interact with data in a variety of ways. Fortunately, you can use Django to build a single project that serves a dynamic website as well as a set of mobile apps. Django is Python’s most popular web framework, a set of tools designed for building interactive web applications. In this chapter, you’ll learn how to use Django to build a project called Learning Log, an online journal system that lets you keep track of information you’ve learned about different topics.

We’ll write a specification ...