Dustin Ingram - PEP 572: The Walrus Operator

In this talk, we'll learn about a highly controversial change to Python syntax, the rationale for it, and the fallout as the result of it.

Along the way we'll go in-depth on how new ideas about Python are proposed, discussed, and become part of the language, what's unique about Python's process compared to other open source projects, and recent developments and what they mean for the future of the wider Python community.

https://us.pycon.org/2019/schedule/presentation/195/

Transcript

1. PEP 572 THE WALRUS OPERATOR ~ DUSTIN INGRAM PYCON US 2019 @di_codes
2. HI, I'M DUSTIN @di_codes
3. PEP 572 @di_codes
4. PYTHON GOVERNANCE @di_codes
5. BDFL BENEVOLENT DICTATOR FOR LIFE @di_codes
7. PEP PYTHON ENHANCEMENT PROPOSAL @di_codes
9. PEP 8 STYLE GUIDE FOR PYTHON CODE @di_codes
10. PEP 8 STYLE GUIDE FOR PYTHON CODE AUTHOR: GUIDO VAN ROSSUM @di_codes
11. PEP 20 THE ZEN OF PYTHON @di_codes
12. PEP 20 THE ZEN OF PYTHON AUTHOR: TIM PETERS @di_codes
13. PEP 566 METADATA FOR PYTHON SOFTWARE PACKAGES 2.1 @di_codes
14. PEP 566 METADATA FOR PYTHON SOFTWARE PACKAGES 2.1 AUTHOR: DUSTIN INGRAM @di_codes
15. 1) DRAFT 2) ACCEPTANCE 3) IMPLEMENTATION @di_codes
16. 1) DRAFT 2) ACCEPTANCE 3) IMPLEMENTATION @di_codes
17. 1) DRAFT 2) ACCEPTANCE 3) IMPLEMENTATION @di_codes
18. BDFL DELEGATES @di_codes
19. @di_codes
20. PEP 572 ASSIGNMENT EXPRESSIONS @di_codes
21. := @di_codes
24. EXAMPLES @di_codes
25. BALANCING LOC AND BIG O() @di_codes
26. foo = [f(x), f(x)**2, f(x)**3] @di_codes
27. y = f(x) foo = [y, y**2, y**3] @di_codes
28. foo = [y := f(x), y**2, y**3] @di_codes
29. AVOIDING INEFFICIENT COMPREHENSIONS @di_codes
30. results = [] for x in data: result = f(x) if result: results.append(result) @di_codes
31. results = [ f(x) for x in data if f(x) ] @di_codes
32. results = [ y for x in data if (y := f(x)) ] @di_codes
33. UNNECESSARY VARIABLES IN SCOPE @di_codes
34. match = pattern.search(data) if match: do_something(match) @di_codes
35. if (match := pattern.search(data)): do_something(match) @di_codes
36. PROCESSING STREAMS IN CHUNKS @di_codes
37. chunk = file.read(8192) while chunk: process(chunk) chunk = file.read(8192) @di_codes
38. while chunk := file.read(8192): process(chunk) @di_codes
39. WHY? @di_codes
40. FEWER LINES ARE BETTER @di_codes
41. y = f(x) foo = [y, y**2, y**3] @di_codes
42. foo = [y := f(x), y**2, y**3] @di_codes
43. FEWER LINES ARE MORE EFFICIENT? @di_codes
44. match = re.match(data) group = match.group(1) if match else None @di_codes
45. group = re.match(data).group(1) if re.match(data) else None @di_codes
46. group = match.group(1) if (match := re.match(data)) else None @di_codes
47. = @di_codes
48. x = y = z = 0 # Yes (z := (y := (x := 0))) # No @di_codes
49. a[i] = x # Yes a[i] := x # No @di_codes
50. self.rest = [] # Yes self.rest := [] # No @di_codes
51. x = 1, 2 # Sets x to (1, 2) (x := 1, 2) # Sets x to 1 @di_codes
52. total += tax # Yes total +:= tax # No @di_codes
53. +:= @di_codes
56. PEP 572 @di_codes
57. RECEPTION @di_codes
58. BACKWARDS COMPATIBILITY "WHERE WILL THIS WORK?" @di_codes
59. TEACHABILITY "WHAT DO WE CALL THIS?" @di_codes
60. ATTRACTIVENESS "IT'S JUST UGLY!" @di_codes
64. TIM PETERS: "THE CURRENT PROPOSAL WOULD HAVE ALLOWED A MODEST BUT CLEAR IMPROVEMENT IN QUITE A FEW BITS OF CODE." @di_codes
65. BARRY WARSAW: "SINCE IT CHANGES THE SYNTAX OF THE LANGUAGE, PEOPLE TEND TO FOCUS ON THAT WITHOUT UNDERSTANDING THE DEEPER SEMANTIC ISSUES." @di_codes
66. ŁUKASZ LANGA: "DICTATORS SHOULD DICTATE" @di_codes
67. GUIDO VAN ROSSUM: HAD TO STOP READING THE THREADS SO HE WOULDN'T "GO INSANE" @di_codes
78. DICTATORS ARE PEOPLE TOO @di_codes
79. MAINTAINERS ARE PEOPLE TOO @di_codes
80. PEOPLE ARE PEOPLE TOO @di_codes
81. QUESTIONS @di_codes
82. WHAT DOES THIS MEAN FOR PYTHON? @di_codes
83. @di_codes
84. @di_codes
85. @di_codes
86. @di_codes
87. IT'S GOING TO BE OK @di_codes
88. PEP 8000 PYTHON LANGUAGE GOVERNANCE PROPOSAL OVERVIEW @di_codes
89. PEP 8001 PYTHON GOVERNANCE VOTING PROCESS @di_codes
90. PEP 8002 OPEN SOURCE GOVERNANCE SURVEY @di_codes
91. ▸ PEP 8010 - The Technical Leader Governance Model ▸ PEP 8011 - Python Governance Model Lead by Trio of Pythonistas ▸ PEP 8012 - The Community Governance Model ▸ PEP 8013 - The External Governance Model ▸ PEP 8014 - The Commons Governance Model ▸ PEP 8015 - Organization of the Python community ▸ PEP 8016 - The Steering Council Model @di_codes
92. VOTE DEC 1ST - 16TH, 2018 @di_codes
94. PEP 8016 STEERING COUNCIL MODEL @di_codes
95. VOTE JAN 21ST - FEB 4TH, 2019 @di_codes
96. . . . @di_codes
101. Q&A @di_codes
102. WILL THIS BECOME PART OF PYTHON? @di_codes
103. IT ALREADY HAS (IN 3.8) @di_codes
104. BUT I DON'T LIKE IT! @di_codes
105. THEN DON'T WRITE IT! @di_codes
106. IS GUIDO COMING BACK? @di_codes
107. TO PYTHON? @di_codes
108. YES! @di_codes
109. AS BDFL? @di_codes
110. NOPE @di_codes
111. WILL THIS HAPPEN AGAIN? @di_codes
112. WILL ANOTHER PEP BE THIS CONTROVERSIAL? @di_codes
113. PROBABLY NOT @di_codes
114. WILL PEOPLE BE NEGATIVE ON THE INTERNET? @di_codes
115. ¯\_(ϑ)_/¯ @di_codes
117. THANKS! @DI_CODES