第1页 / 共299页
第2页 / 共299页
第3页 / 共299页
第4页 / 共299页
第5页 / 共299页
第6页 / 共299页
第7页 / 共299页
第8页 / 共299页
Python Tricks A Buffet of Awesome Python Features.pdf
Contents
Foreword
Introduction
What's a Python Trick?
What This Book Will Do for You
How to Read This Book
Patterns for Cleaner Python
Covering Your A** With Assertions
Complacent Comma Placement
Context Managers and the with Statement
Underscores, Dunders, and More
A Shocking Truth About String Formatting
The Zen of Python Easter Egg
Effective Functions
Python's Functions Are First-Class
Lambdas Are Single-Expression Functions
The Power of Decorators
Fun With *args and **kwargs
Function Argument Unpacking
Nothing to Return Here
Classes & OOP
Object Comparisons: is vs ==
String Conversion (Every Class Needs a __repr__)
Defining Your Own Exception Classes
Cloning Objects for Fun and Profit
Abstract Base Classes Keep Inheritance in Check
What Namedtuples Are Good For
Class vs Instance Variable Pitfalls
Instance, Class, and Static Methods Demystified
Common Data Structures in Python
Dictionaries, Maps, and Hashtables
Array Data Structures
Records, Structs, and Data Transfer Objects
Sets and Multisets
Stacks (LIFOs)
Queues (FIFOs)
Priority Queues
Looping & Iteration
Writing Pythonic Loops
Comprehending Comprehensions
List Slicing Tricks and the Sushi Operator
Beautiful Iterators
Generators Are Simplified Iterators
Generator Expressions
Iterator Chains
Dictionary Tricks
Dictionary Default Values
Sorting Dictionaries for Fun and Profit
Emulating Switch/Case Statements With Dicts
The Craziest Dict Expression in the West
So Many Ways to Merge Dictionaries
Dictionary Pretty-Printing
Pythonic Productivity Techniques
Exploring Python Modules and Objects
Isolating Project Dependencies With Virtualenv
Peeking Behind the Bytecode Curtain
Closing Thoughts
Free Weekly Tips for Python Developers
PythonistaCafe: A Community for Python Developers
Python Tricks: The Book
Dan Bader
For online information and ordering of this and other books by Dan
Bader, please visit dbader.org. For more information, please contact
Dan Bader at mail@dbader.org.
Copyright © Dan Bader (dbader.org), 2016–2017
ISBN: 9781775093305 (paperback)
ISBN: 9781775093312 (electronic)
Cover design by Anja Pircher Design (anjapircher.com)
“Python” and the Python logos are trademarks or registered trade-
marks of the Python Software Foundation, used by Dan Bader with
permission from the Foundation.
Thank you for downloading this ebook. This ebook is licensed for your
personal enjoyment only. This ebook may not be re-sold or given away
to other people. If you would like to share this book with another per-
son, please purchase an additional copy for each recipient. If you’re
reading this book and did not purchase it, or it was not purchased
for your use only, then please return to dbader.org/pytricks-book and
purchase your own copy. Thank you for respecting the hard work be-
hind this book.
Updated 2017-10-27 I would like to thank Michael Howitz, Johnathan
Willitts, Julian Orbach, Johnny Giorgis, Bob White, Daniel Meyer,
Michael Stueben, Smital Desai, Andreas Kreisig, David Perkins, Jay
Prakash Singh, and Ben Felder for their excellent feedback.
What Pythonistas Say About Python Tricks: The Book
”I love love love the book. It’s like having a seasoned tutor explaining,
well, tricks! I’m learning Python on the job and I’m coming from pow-
ershell, which I learned on the job—so lots of new, great stuff. When-
ever I get stuck in Python (usually with flask blueprints or I feel like my
code could be more Pythonic) I post questions in our internal Python
chat room.
I’m often amazed at some of the answers coworkers give me. Dict com-
prehensions, lambdas, and generators often pepper their feedback. I
am always impressed and yet flabbergasted at how powerful Python
is when you know these tricks and can implement them correctly.
Your book was exactly what I wanted to help get me from a bewildered
powershell scripter to someone who knows how and when to use these
Pythonic ‘tricks’ everyone has been talking about.
As someone who doesn’t have my degree in CS it’s nice to have the text
to explain things that others might have learned when they were clas-
sically educated. I am really enjoying the book and am subscribed to
the emails as well, which is how I found out about the book.”
— Daniel Meyer, Sr. Desktop Administrator at Tesla Inc.
”I first heard about your book from a co-worker who wanted to
trick me with your example of how dictionaries are built.
I was
almost 100% sure about the reason why the end product was a much
smaller/simpler dictionary but I must confess that I did not expect
the outcome :)
He showed me the book via video conferencing and I sort of skimmed
through it as he flipped the pages for me, and I was immediately curi-
ous to read more.
That same afternoon I purchased my own copy and proceeded to read
your explanation for the way dictionaries are created in Python and
later that day, as I met a different co-worker for coffee, I used the same
trick on him :)
He then sprung a different question on the same principle, and be-
cause of the way you explained things in your book, I was able tonot*
guess the result but correctly answer what the outcome would be. That
means that you did a great job at explaining things :)*
I am not new in Python and some of the concepts in some of the chap-
ters are not new to me, but I must say that I do get something out of
every chapter so far, so kudos for writing a very nice book and for do-
ing a fantastic job at explaining concepts behind the tricks! I’m very
much looking forward to the updates and I will certainly let my friends
and co-workers know about your book.”
— Og Maciel, Python Developer at Red Hat
”I really enjoyed reading Dan’s book. He explains important Python
aspects with clear examples (using two twin cats to explain ‘is‘ vs ‘==‘
for example).
It is not just code samples, it discusses relevant implementation details
comprehensibly. What really matters though is that this book makes
you write better Python code!
The book is actually responsible for recent new good Python habits I
picked up, for example: using custom exceptions and ABC’s (I found
Dan’s blog searching for abstract classes.) These new learnings alone
are worth the price.”
— Bob Belderbos, Engineer at Oracle & Co-Founder of PyBites
Contents
Contents
Foreword
1
Introduction
1.1 What’s a Python Trick? .
.
1.2 What This Book Will Do for You .
1.3 How to Read This Book .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
2 Patterns for Cleaner Python
Covering Your A** With Assertions .
.
.
2.1
2.2 Complacent Comma Placement .
.
2.3 Context Managers and the with Statement .
2.4 Underscores, Dunders, and More .
.
2.5 A Shocking Truth About String Formatting .
2.6
.
“The Zen of Python” Easter Egg .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3 Effective Functions
.
.
Python’s Functions Are First-Class .
3.1
.
3.2 Lambdas Are Single-Expression Functions .
.
3.3 The Power of Decorators .
.
.
3.4 Fun With *args and **kwargs .
3.5
Function Argument Unpacking .
.
.
.
3.6 Nothing to Return Here .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
6
6
9
11
11
13
14
15
16
25
29
36
48
56
57
58
68
73
86
91
94
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
Contents
4 Classes & OOP
.
.
.
.
.
.
.
4.1 Object Comparisons: “is” vs “==” .
.
4.2
String Conversion (Every Class Needs a __repr__)
4.3 Defining Your Own Exception Classes
.
4.4 Cloning Objects for Fun and Profit
.
.
4.5 Abstract Base Classes Keep Inheritance in Check .
.
4.6 What Namedtuples Are Good For .
4.7 Class vs Instance Variable Pitfalls .
.
4.8 Instance, Class, and Static Methods Demystified .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
5 Common Data Structures in Python
.
5.1 Dictionaries, Maps, and Hashtables
5.2 Array Data Structures .
.
.
5.3 Records, Structs, and Data Transfer Objects .
5.4
.
.
5.5
.
.
5.6 Queues (FIFOs) .
5.7
Priority Queues .
.
Sets and Multisets .
.
Stacks (LIFOs)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
6 Looping & Iteration
.
.
.
.
.
.
.
.
.
6.1 Writing Pythonic Loops .
.
.
6.2 Comprehending Comprehensions
6.3 List Slicing Tricks and the Sushi Operator
.
6.4 Beautiful Iterators .
.
.
6.5 Generators Are Simplified Iterators
6.6 Generator Expressions
.
.
.
.
.
6.7
Iterator Chains
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
7 Dictionary Tricks
.
.
.
.
.
.
.
Sorting Dictionaries for Fun and Profit .
.
7.1 Dictionary Default Values .
7.2
.
7.3 Emulating Switch/Case Statements With Dicts .
7.4 The Craziest Dict Expression in the West .
.
.
.
7.5
7.6 Dictionary Pretty-Printing .
.
.
So Many Ways to Merge Dictionaries .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
97
98
.
101
.
111
.
116
.
.
124
. 128
. 136
. 143
153
.
156
. 163
.
173
. 185
. 189
.
195
. 201
205
. 206
. 210
. 214
. 218
. 231
. 239
. 246
250
. 251
. 255
. 259
. 264
. 271
. 274
7
相关推荐
2023年江西萍乡中考道德与法治真题及答案.doc
2012年重庆南川中考生物真题及答案.doc
2013年江西师范大学地理学综合及文艺理论基础考研真题.doc
2020年四川甘孜小升初语文真题及答案I卷.doc
2020年注册岩土工程师专业基础考试真题及答案.doc
2023-2024学年福建省厦门市九年级上学期数学月考试题及答案.doc
2021-2022学年辽宁省沈阳市大东区九年级上学期语文期末试题及答案.doc
2022-2023学年北京东城区初三第一学期物理期末试卷及答案.doc
2018上半年江西教师资格初中地理学科知识与教学能力真题及答案.doc
2012年河北国家公务员申论考试真题及答案-省级.doc
2020-2021学年江苏省扬州市江都区邵樊片九年级上学期数学第一次质量检测试题及答案.doc
2022下半年黑龙江教师资格证中学综合素质真题及答案.doc
