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Python in a Nutshell, 4th Edition

by Alex Martelli, Anna Martelli Ravenscroft, Steve Holden, Paul McGuire

January 2023

Intermediate to advanced

738 pages

21h 28m

English

O'Reilly Media, Inc.

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Preface
How To Use This BookPart I, Getting Started with PythonPart II, Core Python Language and Built-insPart III, Python Library and Extension ModulesPart IV, Network and Web ProgrammingPart V, Extending, Distributing, and Version Upgrade and MigrationConventions Used in This BookReference ConventionsVersion ConventionsTypographic ConventionsUsing Code ExamplesO’Reilly Online LearningHow to Contact UsAcknowledgments
1. Introduction to Python
The Python LanguageThe Python Standard Library and Extension ModulesPython ImplementationsCPythonPyPyChoosing Between CPython, PyPy, and Other ImplementationsOther Developments, Implementations, and DistributionsLicensing and Price IssuesPython Development and VersionsPython ResourcesDocumentationCommunityInstallationInstalling Python from BinariesInstalling Python from Source CodeMicrosoft WindowsUnix-Like Platforms
2. The Python Interpreter
The python ProgramEnvironment VariablesCommand-Line Syntax and OptionsThe Windows py LauncherThe PyPy InterpreterInteractive SessionsPython Development EnvironmentsIDLEOther Python IDEsFree Text Editors with Python SupportTools for Checking Python ProgramsRunning Python ProgramsRunning Python in the BrowserPyScriptJupyter
3. The Python Language
Lexical StructureLines and IndentationCharacter SetsTokensStatementsData TypesNumbersSequencesSetsDictionariesNoneEllipsis (...)CallablesBoolean ValuesVariables and Other ReferencesVariablesAssignment Statementsdel StatementsExpressions and OperatorsComparison ChainingShort-Circuiting OperatorsAssignment ExpressionsNumeric OperationsNumeric ConversionsArithmetic OperationsBitwise Operations on IntegersSequence OperationsSequences in GeneralStringsTuplesListsSet OperationsSet MembershipSet MethodsDictionary OperationsDictionary MembershipIndexing a DictionaryDictionary MethodsControl Flow StatementsThe if StatementThe match StatementThe while StatementThe for StatementThe break StatementThe continue StatementThe else Clause on Loop StatementsThe pass StatementThe try and raise StatementsThe with StatementFunctionsDefining Functions: The def StatementParametersAttributes of Function ObjectsFunction AnnotationsThe return StatementCalling FunctionsNamespaceslambda ExpressionsGeneratorsRecursion
4. Object-Oriented Python
Classes and InstancesPython ClassesThe class StatementThe Class BodyDescriptorsInstancesAttribute Reference BasicsBound and Unbound MethodsInheritanceThe Built-in object TypeClass-Level MethodsProperties__slots____getattribute__Per Instance MethodsInheritance from Built-in TypesSpecial MethodsGeneral-Purpose Special MethodsSpecial Methods for ContainersAbstract Base ClassesSpecial Methods for Numeric ObjectsDecoratorsMetaclassesAlternatives to Custom Metaclasses for Simple Class CustomizationHow Python Determines a Class’s MetaclassHow a Metaclass Creates a ClassData ClassesEnumerated Types (Enums)
5. Type Annotations
HistoryType-Checking UtilitiesmypyOther Type CheckersType Annotation SyntaxThe typing ModuleTypesType Expression ParametersAbstract Base ClassesProtocolsUtilities and DecoratorsDefining Custom TypesUsing Type Annotations at RuntimeHow to Add Type Annotations to Your CodeAdding Type Annotations to New CodeAdding Type Annotations to Existing Code (Gradual Typing)Using .pyi Stub FilesSummary
6. Exceptions
The try Statementtry/excepttry/finallytry/except/finallyThe raise StatementThe with Statement and Context ManagersGenerators and ExceptionsException PropagationException ObjectsThe Hierarchy of Standard ExceptionsStandard Exception ClassesCustom Exception ClassesCustom Exceptions and Multiple InheritanceOther Exceptions Used in the Standard LibraryExceptionGroup and except*Error-Checking StrategiesLBYL Versus EAFPHandling Errors in Large ProgramsLogging ErrorsThe assert Statement
7. Modules and Packages
Module ObjectsThe import StatementThe from StatementModule LoadingBuilt-in ModulesSearching the Filesystem for a ModuleThe Main ProgramReloading ModulesCircular ImportsCustom ImportersPackagesSpecial Attributes of Package ObjectsAbsolute Versus Relative ImportsDistribution Utilities (distutils) and setuptoolsPython EnvironmentsEnter the Virtual EnvironmentWhat Is a Virtual Environment?Creating and Deleting Virtual EnvironmentsWorking with Virtual EnvironmentsManaging Dependency RequirementsOther Environment Management SolutionsBest Practices with Virtualenvs
8. Core Built-ins and Standard Library Modules
Built-in TypesBuilt-in FunctionsThe sys ModuleThe copy ModuleThe collections ModuleChainMapCounterOrderedDictdefaultdictdequeThe functools ModuleThe heapq ModuleThe Decorate–Sort–Undecorate IdiomThe argparse ModuleThe itertools Module
9. Strings and Things
Methods of String ObjectsThe string ModuleString FormattingFormatted String Literals (F-Strings)Formatting Using format CallsValue ConversionValue Formatting: The Format SpecifierNested Format SpecificationsFormatting of User-Coded ClassesLegacy String Formatting with %Format Specifier SyntaxText Wrapping and FillingThe pprint ModuleThe reprlib ModuleUnicodeThe codecs ModuleThe unicodedata Module

10. Regular Expressions
Regular Expressions and the re ModuleREs and bytes Versus strPattern String SyntaxCommon Regular Expression IdiomsSets of CharactersAlternativesGroupsOptional FlagsMatch Versus SearchAnchoring at String Start and EndRegular Expression ObjectsMatch ObjectsFunctions of the re ModuleREs and the := OperatorThe Third-Party regex Module
11. File and Text Operations
The io ModuleCreating a File Object with openAttributes and Methods of File ObjectsIteration on File ObjectsFile-Like Objects and PolymorphismThe tempfile ModuleAuxiliary Modules for File I/OThe fileinput ModuleThe struct ModuleIn-Memory Files: io.StringIO and io.BytesIOArchived and Compressed FilesThe tarfile ModuleThe zipfile ModuleThe os ModuleFilesystem OperationsThe os.path ModuleOSError ExceptionsThe errno ModuleThe pathlib ModuleThe stat ModuleThe filecmp ModuleThe fnmatch ModuleThe glob ModuleThe shutil ModuleText Input and OutputStandard Output and Standard ErrorThe print FunctionStandard InputThe getpass ModuleRicher-Text I/OThe readline ModuleConsole I/OInternationalizationThe locale ModuleThe gettext ModuleMore Internationalization Resources
12. Persistence and Databases
SerializationThe csv ModuleThe json ModuleThe pickle ModuleThe shelve ModuleDBM ModulesThe dbm PackageExamples of DBM-Like File UseThe Python Database API (DBAPI)Exception ClassesThread SafetyParameter StyleFactory FunctionsType Description AttributesThe connect FunctionConnection ObjectsCursor ObjectsDBAPI-Compliant ModulesSQLite
13. Time Operations
The time ModuleThe datetime ModuleThe date ClassThe time ClassThe datetime ClassThe timedelta ClassThe tzinfo Abstract ClassThe timezone ClassThe zoneinfo ModuleThe dateutil ModuleThe sched ModuleThe calendar Module
14. Customizing Execution
Per-Site CustomizationTermination FunctionsDynamic Execution and execAvoiding execExpressionscompile and Code ObjectsNever exec or eval Untrusted CodeInternal TypesType ObjectsThe Code Object TypeThe Frame TypeGarbage CollectionThe gc ModuleThe weakref Module
15. Concurrency: Threads and Processes
Threads in PythonThe threading ModuleThread ObjectsThread Synchronization ObjectsThread Local StorageThe queue ModuleThe multiprocessing ModuleDifferences Between multiprocessing and threadingSharing State: Classes Value, Array, and ManagerProcess PoolsThe concurrent.futures ModuleThreaded Program ArchitectureProcess EnvironmentRunning Other ProgramsUsing the Subprocess ModuleRunning Other Programs with the os ModuleThe mmap ModuleMethods of mmap ObjectsUsing mmap Objects for IPC
16. Numeric Processing
Floating-Point ValuesThe math and cmath ModulesThe statistics ModuleThe operator ModuleRandom and Pseudorandom NumbersThe random ModuleCrypto-Quality Random Numbers: The secrets ModuleThe fractions ModuleThe decimal ModuleArray ProcessingThe array ModuleExtensions for Numeric Array Computation
17. Testing, Debugging, and Optimizing
TestingUnit Testing and System TestingThe doctest ModuleThe unittest ModuleTesting with nose2Testing with pytestDebuggingBefore You DebugThe inspect ModuleThe traceback ModuleThe pdb ModuleOther Debugging ModulesThe warnings ModuleClassesObjectsFiltersFunctionsOptimizationDeveloping a Fast-Enough Python ApplicationBenchmarkingLarge-Scale OptimizationProfilingSmall-Scale Optimization
18. Networking Basics
The Berkeley Socket InterfaceSocket AddressesClient/Server ComputingThe socket ModuleSocket ObjectsA Connectionless Socket ClientA Connectionless Socket ServerA Connection-Oriented Socket ClientA Connection-Oriented Socket ServerTransport Layer SecuritySSLContext
19. Client-Side Network Protocol Modules
Email ProtocolsThe poplib ModuleThe smtplib ModuleHTTP and URL ClientsURL AccessThe urllib PackageThe Third-Party requests PackageOther Network Protocols
20. Serving HTTP
http.serverWSGIWSGI ServersASGIPython Web Frameworks“Full-Stack” Versus “Lightweight” FrameworksA Few Popular Full-Stack FrameworksConsiderations When Using Lightweight FrameworksA Few Popular Lightweight Frameworks
21. Email, MIME, and Other Network Encodings
MIME and Email Format HandlingFunctions in the email PackageThe email.message ModuleThe email.Generator ModuleCreating MessagesThe email.encoders ModuleThe email.utils ModuleExample Uses of the email PackageEncoding Binary Data as ASCII TextThe base64 ModuleThe quopri ModuleThe uu Module
22. Structured Text: HTML
The html.entities ModuleThe BeautifulSoup Third-Party PackageThe BeautifulSoup ClassThe Navigable Classes of bs4bs4 find… Methods (aka Search Methods)bs4 CSS SelectorsAn HTML Parsing Example with BeautifulSoupGenerating HTMLEditing and Creating HTML with bs4Building HTML with bs4TemplatingThe jinja2 Package
23. Structured Text: XML
ElementTreeThe Element ClassThe ElementTree ClassFunctions in the ElementTree ModuleParsing XML with ElementTree.parseSelecting Elements from an ElementTreeEditing an ElementTreeBuilding an ElementTree from ScratchParsing XML Iteratively
24. Packaging Programs and Extensions
What We Don’t Cover in This ChapterA Brief History of Python PackagingOnline Material
25. Extending and Embedding Classic Python
Online Material
26. v3.7 to v3.n Migration
Significant Changes in Python Through 3.11Planning a Python Version UpgradeChoosing a Target VersionScoping the WorkApplying the Code ChangesUpgrade Automation Using pyupgradeMultiversion TestingUse a Controlled Deployment ProcessHow Often Should You Upgrade?Summary
Appendix. New Features and Changes in Python 3.7 Through 3.11
Python 3.7Python 3.8Python 3.9Python 3.10Python 3.11
Index
About the Authors

Content preview from Python in a Nutshell, 4th Edition

Appendix. New Features and Changes in Python 3.7 Through 3.11

The following tables enumerate language and standard library changes in Python versions 3.7 through 3.11 that are most likely to be found in Python code. Use these tables to plan your upgrade strategy, as constrained by your exposure to breaking changes in your codebase.

Settings for Online Reading

To better view these tables you may need to reduce the font size in the settings of your device or content viewer.

The following types of changes are considered to be “breaking” and are marked with a ! symbol in the last column:

Introduces new keywords or built-ins (which may clash with names used in existing Python source code)
Removes a method from a stdlib module or built-in type
Changes a built-in or stdlib method signature in a way that is not backward-compatible (such as removing a parameter, or renaming a named parameter)

New warnings (including DeprecatedWarning) are also shown as “breaking,” but marked with a * symbol in the last column.

Also see the table of proposed deprecations and removals from the standard library (“dead batteries”) in PEP 594, which lists modules that are slated for deprecation or removal, the versions in which these changes are scheduled to be made (beginning with Python 3.12), and recommended replacements.

Python 3.7

The following table summarizes changes in Python version 3.7. For further details, see “What’s New in Python 3.7” in the online docs.

Python 3.7	Added	Deprecated ...

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