Chapter 1 Pythonic Thinking 1 Item 1: Know Which Version of Python You’re Using 1 Item 2: Follow the PEP 8 Style Guide 2 Item 3: Know the Differences Between bytes and str 5 Item 4: Prefer Interpolated F-Strings Over C-style Format Strings and str.format 11 Item 5: Write Helper Functions Instead of Complex Expressions 21 Item 6: Prefer Multiple Assignment Unpacking Over Indexing 24 Item 7: Prefer enumerate Over range 28 Item 8: Use zip to Process Iterators in Parallel 30 Item 9: Avoid else Blocks After for and while Loops 32 Item 10: Prevent Repetition with Assignment Expressions 35 Chapter 2 Lists and Dictionaries 43 Item 11: Know How to Slice Sequences 43 Item 12: Avoid Striding and Slicing in a Single Expression 46 Item 13: Prefer Catch-All Unpacking Over Slicing 48 Item 14: Sort by Complex Criteria Using the key Parameter 52 Item 15: Be Cautious When Relying on dict Insertion Ordering 58 Item 16: Prefer get Over in and KeyError to Handle Missing Dictionary Keys 65 Item 17: Prefer defaultdict Over setdefault to Handle Missing Items in Internal State 70 Item 18: Know How to Construct Key-Dependent Default Values with __missing__ 73 Chapter 3 Functions 77 Item 19: Never Unpack More Than Three Variables When Functions Return Multiple Values 77 Item 20: Prefer Raising Exceptions to Returning None 80 Item 21: Know How Closures Interact with Variable Scope 83 Item 22: Reduce Visual Noise with Variable Positional Arguments 87 Item 23: Provide Optional Behavior with Keyword Arguments 90 Item 24: Use None and Docstrings to Specify Dynamic Default Arguments 94 Item 25: Enforce Clarity with Keyword-Only and Positional-Only Arguments 97 Item 26: Define Function Decorators with functools.wraps 102 Chapter 4 Comprehensions and Generators 107 Item 27: Use Comprehensions Instead of map and filter 107 Item 28: Avoid More Than Two Control Subexpressions in Comprehensions 109 Item 29: Avoid Repeated Work in Comprehensions by Using Assignment Expressions 111 Item 30: Consider Generators Instead of Returning Lists 114 Item 31: Be Defensive When Iterating Over Arguments 117 Item 32: Consider Generator Expressions for Large List Comprehensions 122 Item 33: Compose Multiple Generators with yield from 124 Item 34: Avoid Injecting Data into Generators with send 127 Item 35: Avoid Causing State Transitions in Generators with throw 133 Item 36: Consider itertools for Working with Iterators and Generators 138 Chapter 5 Classes and Interfaces 145 Item 37: Compose Classes Instead of Nesting Many Levels of Built-in Types 145 Item 38: Accept Functions Instead of Classes for Simple Interfaces 152 Item 39: Use @classmethod Polymorphism to Construct Objects Generically 155 Item 40: Initialize Parent Classes with super 160 Item 41: Consider Composing Functionality with Mix-in Classes 165 Item 42: Prefer Public Attributes Over Private Ones 170 Item 43: Inherit from collections.abc for Custom Container Types 175 Chapter 6 Metaclasses and Attributes 181 Item 44: Use Plain Attributes Instead of Setter and Getter Methods 181 Item 45: Consider @property Instead of Refactoring Attributes 186 Item 46: Use Descriptors for Reusable @property Methods 190 Item 47: Use __getattr__, __getattribute__, and __setattr__ for Lazy Attributes 195 Item 48: Validate Subclasses with __init_subclass__ 201 Item 49: Register Class Existence with __init_subclass__ 208 Item 50: Annotate Class Attributes with __set_name__ 214 Item 51: Prefer Class Decorators Over Metaclasses for Composable Class Extensions 218 Chapter 7 Concurrency and Parallelism 225 Item 52: Use subprocess to Manage Child Processes 226 Item 53: Use Threads for Blocking I/O, Avoid for Parallelism 230 Item 54: Use Lock to Prevent Data Races in Threads 235 Item 55: Use Queue to Coordinate Work Between Threads 238 Item 56: Know How to Recognize When Concurrency Is Necessary 248 Item 57: Avoid Creating New Thread Instances for On-demand Fan-out 252 Item 58: Understand How Using Queue for Concurrency Requires Refactoring 257 Item 59: Consider ThreadPoolExecutor When Threads Are Necessary for Concurrency 264 Item 60: Achieve Highly Concurrent I/O with Coroutines 266 Item 61: Know How to Port Threaded I/O to asyncio 271 Item 62: Mix Threads and Coroutines to Ease the Transition to asyncio 282 Item 63: Avoid Blocking the asyncio Event Loop to Maximize Responsiveness 289 Item 64: Consider concurrent.futures for True Parallelism 292 Chapter 8 Robustness and Performance 299 Item 65: Take Advantage of Each Block in try/except /else/finally 299 Item 66: Consider contextlib and with Statements for Reusable try/finally Behavior 304 Item 67: Use datetime Instead of time for Local Clocks 308 Item 68: Make pickle Reliable with copyreg 312 Item 69: Use decimal When Precision Is Paramount 319 Item 70: Profile Before Optimizing 322 Item 71: Prefer deque for Producer?CConsumer Queues 326 Item 72: Consider Searching Sorted Sequences with bisect 334 Item 73: Know How to Use heapq for Priority Queues 336 Item 74: Consider memoryview and bytearray for Zero-Copy Interactions with bytes 346 Chapter 9 Testing and Debugging 353 Item 75: Use repr Strings for Debugging Output 354 Item 76: Verify Related Behaviors in TestCase Subclasses 357 Item 77: Isolate Tests from Each Other with setUp, tearDown, setUpModule, and tearDownModule 365 Item 78: Use Mocks to Test Code with Complex Dependencies 367 Item 79: Encapsulate Dependencies to Facilitate Mocking and Testing 375 Item 80: Consider Interactive Debugging with pdb 379 Item 81: Use tracemalloc to Understand Memory Usage and Leaks 384 Chapter 10 Collaboration 389 Item 82: Know Where to Find Community-Built Modules 389 Item 83: Use Virtual Environments for Isolated and Reproducible Dependencies 390 Item 84: Write Docstrings for Every Function, Class, and Module 396 Item 85: Use Packages to Organize Modules and Provide Stable APIs 401 Item 86: Consider Module-Scoped Code to Configure Deployment Environments 406 Item 87: Define a Root Exception to Insulate Callers from APIs 408 Item 88: Know How to Break Circular Dependencies 413 Item 89: Consider warnings to Refactor and Migrate Usage 418 Item 90: Consider Static Analysis via typing to Obviate Bugs 425 Index 435
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