Pydon'ts: Write elegant Python code

Foreword....12 Pydon’t disrespect the Zen of Python....13 Zen of Python....14 References....15 Zip up....16 Introduction....16 How zip works....17 Zip is lazy....18 Three is a crowd....19 Mismatched lengths....19 Create a dictionary with zip....20 Examples in code....20 Conclusion....23 References....24 Enumerate me....25 Introduction....25 How enumerate works....26 Optional start argument....27 Unpacking when iterating....27 Examples in code....29 Conclusion....34 References....35 Chaining comparison operators....36 Introduction....37 Chaining of comparison operators....37 Pitfalls....38 Ugly chains....39 Examples in code....40 Conclusion....41 References....41 Boolean short-circuiting....42 Introduction....42 Return values of the and and or operators....43 Short-circuiting....44 Short-circuiting in plain English....46 all and any....47 Short-circuiting in chained comparisons....47 Examples in code....47 Conclusion....56 References....56 set and frozenset....58 Introduction....58 (Mathematical) sets....59 (Common) Operations on sets....60 Differences between set and frozenset....63 What are sets used for?....65 Examples in code....66 Conclusion....70 References....70 List comprehensions 101....71 Introduction....71 What is a list comprehension?....72 A loop that builds a list....72 Filtering data in a list comprehension....74 List comprehensions from first principles....76 Full anatomy of a list comprehension....77 Advantages of list comprehensions....80 Examples in code....81 Conclusion....85 References....85 Sequence indexing....86 Introduction....86 Sequence indexing....87 Maximum legal index and index errors....88 Negative indices....88 Indexing idioms....90 To index or not to index?....90 Best practices in code....91 Conclusion....94 Idiomatic sequence slicing....96 Introduction....96 Slicing syntax....97 What to slice?....98 Slicing from the beginning....99 Slicing until the end....100 Slicing with negative indices....100 Slicing and range....101 Idiomatic slicing patterns....102 Empty slices....103 More empty slices....104 Examples in code....104 Conclusion....107 References....108 String formatting comparison....109 Introduction....109 String formatting rationale....110 Three string formatting methods....111 Value conversion....112 Alignment....113 Named placeholders....114 Accessing nested data structures....114 Parametrised formatting....115 Custom formatting....116 Examples in code....117 Conclusion....118 References....119 Truthy, Falsy, and bool....120 “Truthy” and “Falsy”....122 The __bool__ dunder method....123 Remarks....124 Examples in code....125 Conclusion....128 References....128 Assignment expressions and the walrus operator :=....129 Walrus operator and assignment expressions....129 Examples in code....130 Conclusion....133 References....133 String translate and maketrans methods....134 Introduction....134 str.translate....135 Non-equivalence to str.replace....137 Generic translation tables....138 str.maketrans....139 Examples in code....141 Conclusion....145 References....146 Conditional expressions....147 Introduction....147 What is a conditional expression?....148 Rationale....150 Short-circuiting....151 Conditional expressions and if statements....153 Precedence....156 Conditional expressions that evaluate to Booleans....157 Examples in code....158 Conclusion....159 References....160 Dunder methods....161 Introduction....161 What are dunder methods?....162 List of dunder methods and their interactions....164 Exploring a dunder method....167 Conclusion....169 References....170 Overloading arithmetic operators with dunder methods....171 Introduction....173 The example we will be using....174 Your first arithmetic dunder method....174 The dunder methods for the unary arithmetic operations....176 The dunder methods for binary arithmetic operations....179 Addition and the dunder method __add__....179 Adding validation to your dunder methods....180 Using NotImplemented to flag operations you don’t support....181 Extending your dunder method to more types....183 Reflected dunder methods....185 Implementing reflected dunder methods....185 Augmented arithmetic assignment....190 Full implementation of all arithmetic dunder methods....191 Exercises....216 Conclusion....216 References....217 str and repr....218 str and repr....220 The __str__ and __repr__ dunder methods....220 Examples in code....221 Conclusion....223 References....223 Deep unpacking....224 Introduction....224 Assignments....225 Examples in code....227 Conclusion....229 References....229 Unpacking with starred assignments....231 Starred Assignment....232 Examples in code....233 References....235 Structural pattern matching tutorial....236 Introduction....237 Structural pattern matching Python could already do....237 Your first match statement....237 Pattern matching the basic structure....238 Matching the structure of objects....240 __match_args__....241 Wildcards....242 Naming sub-patterns....244 Traversing recursive structures....245 Conclusion....247 References....247 Structural pattern matching anti-patterns....249 Introduction....250 There should be only one obvious way to do it....250 A short and sweet if statement....250 Be smart(er)....251 Basic mappings....252 Conclusion....257 References....258 Mastering sequence slicing....259 Introduction....259 Slicing step....260 Sequence copying....267 Manipulating mutable sequences....267 More idiomatic slicing....270 Conclusion....273 References....274 Inner workings of sequence slicing....275 Introduction....276 The slice class....276 Getting items from sequences....278 Setting items, deleting items, and container emulation....279 Comma-separated indices and slices....279 Examples in code....280 Conclusion....284 References....284 Properties....286 Introduction....286 What is a property?....287 Common property use cases....289 Properties with setters....293 Property deleters....295 The property descriptor....297 Conclusion....299 References....299 Describing Descriptors....300 Introduction....301 The problem that descriptors solve....301 Your first descriptor....302 Accessing the name of the original attribute....306 Descriptor exercises....309 Descriptor protocol....311 The dunder method __set__....311 Accessing the descriptor objects....315 Built-in descriptors....317 Methods and descriptors....326 Data and non-data descriptors....329 Complete descriptor example: attribute validation....333 Descriptors in the standard library....334 Conclusion....335 References....335 Boost your productivity with the REPL....337 Introduction....337 REPL....338 Just fire up the REPL....338 REPL mechanics....338 The last result....342 Getting help from within the REPL....343 Tips for quick hacks....344 Other tools....346 Conclusion....347 References....347 The power of reduce....348 Introduction....348 How reduce works....349 The rabbit hole of the built-in reductions....350 Why bother?....351 Far-fetched reductions....351 The identity element…....353 Why some people dislike reduce....355 Examples in code....355 Conclusion....357 References....357 Usages of underscore....359 Introduction....359 Recovering last result in the session....360 Prefixes and suffixes for variable names....361 Underscore as a sink....367 Matching everything in the new match statement....369 String localisation....370 Improve number readability....371 Conclusion....372 References....372 name dunder attribute....374 Introduction....374 What is __name__?....375 The module attribute __name__....375 __name__ as an object type attribute....377 Examples in code....379 Conclusion....383 References....383 Pass-by-value, reference, and assignment....384 Introduction....386 Is Python pass-by-value?....386 Is Python pass-by-reference?....387 Python object model....388 Python is pass-by-assignment....392 Making copies....393 Examples in code....396 Conclusion....400 References....400 Watch out for recursion....401 Introduction....402 Watch out for recursion....402 Examples in code....405 Conclusion....411 References....412 EAFP and LBYL coding styles....413 EAFP and LBYL....413 EAFP instead of LBYL?....414 Conclusion....418 References....418 Bite-sized refactoring....419 Introduction....419 Refactoring....420 What to refactor?....421 Case study....421 Conclusion....428 References....429 Naming matters....430 Introduction....430 Naming conventions....431 PEP 8 recommendations....431 Standard names....433 Verbosity....434 Picking a name....437 Context is key....439 Practical example....439 Conclusion....441 References....442 Does elegance matter?....443 Introduction....443 Beware, opinions ahead....444 Elegance is not a dispensable luxury....444 Don’t write that, that’s unreadable....444 The right tool for the job....445 Optimise for rewrite....446 Conclusion....446 References....447 Code style matters....448 Introduction....449 Code style....449 Tools for your tool belt....450 Conclusion....453 References....453 Why mastering Python is impossible, and why that’s ok....455 Introduction....456 “to master”, verb....456 How to get as close to mastering Python as possible....457 Anecdote with string methods....461 Conclusion....462 References....462 Closing thoughts....463