PEP 498: The Monologue

A presentation at PyCon Canada 2017 in November 2017 in Montreal, QC, Canada by Mariatta

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MARIATTA WIJAYA @mariatta PYCON CANADA 2017 PEP 498: THE MONOLOGUE #PEPtalk

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! You cool people! Who are you? @mariatta PYCON CANADA 2017 #PEPtalk

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Are you … … new to Python? @mariatta PYCON CANADA 2017 #PEPtalk

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Are you … … only aware of one PEP? @mariatta PYCON CANADA 2017 #PEPtalk

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Are you … … using Python < 3.6? @mariatta PYCON CANADA 2017 #PEPtalk

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Who am I? @mariatta PYCON CANADA 2017 #PEPtalk

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Who am I? @mariatta PYCON CANADA 2017 #PEPtalk

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Who am I? @mariatta @mariatta PYCON CANADA 2017 #PEPtalk

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Who am I? @mariatta @mariatta PYCON CANADA 2017 #PEPtalk

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Who am I? @mariatta Software Engineer @mariatta PYCON CANADA 2017 #PEPtalk

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Who am I? @mariatta Software Engineer Python Core Developer @mariatta PYCON CANADA 2017 #PEPtalk

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What’s a PEP? @mariatta PYCON CANADA 2017 #PEPtalk

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P ython E nhancement P roposal @mariatta PYCON CANADA 2017 #PEPtalk

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PEP 1 PEP Purpose and Guideline https://www.python.org/dev/peps/pep-0001 @mariatta PYCON CANADA 2017 #PEPtalk

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pitch to python-ideas @mariatta PYCON CANADA 2017 #PEPtalk

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draft a PEP o ﬃ cial template: PEP 12 @mariatta PYCON CANADA 2017 #PEPtalk

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BDFL Pronouncement @mariatta PYCON CANADA 2017 #PEPtalk

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BDFL Pronouncement % @mariatta PYCON CANADA 2017 #PEPtalk

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BDFL Pronouncement % & @mariatta PYCON CANADA 2017 #PEPtalk

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450 PEPs today 88 rejected @mariatta PYCON CANADA 2017 #PEPtalk

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PEP 498 @mariatta PYCON CANADA 2017 #PEPtalk

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Jul 20 01:12:31 CEST 2015 From: Mike Miller Subject: [python-ideas] Briefer string format https://mail.python.org/pipermail/python-ideas/2015-July/034657.html @mariatta PYCON CANADA 2017 #PEPtalk

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Jul 20 01:12:31 CEST 2015 H a v e l o n g w i s h e d p y t h o n c o u l d f o r m a t s t r i n g s e a s i l y l i k e b a s h o r p e r l d o … a n d t h e n i t h i t m e From: Mike Miller Subject: [python-ideas] Briefer string format https://mail.python.org/pipermail/python-ideas/2015-July/034657.html @mariatta PYCON CANADA 2017 #PEPtalk

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Jul 20 01:12:31 CEST 2015 H a v e l o n g w i s h e d p y t h o n c o u l d f o r m a t s t r i n g s e a s i l y l i k e b a s h o r p e r l d o … a n d t h e n i t h i t m e From: Mike Miller Subject: [python-ideas] Briefer string format c s s t e x t +

f ' { n l } { s e l e c t o r } { s p a c e } { { { n l } ' https://mail.python.org/pipermail/python-ideas/2015-July/034657.html @mariatta PYCON CANADA 2017 #PEPtalk

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Jul 20 01:12:31 CEST 2015 H a v e l o n g w i s h e d p y t h o n c o u l d f o r m a t s t r i n g s e a s i l y l i k e b a s h o r p e r l d o … a n d t h e n i t h i t m e From: Mike Miller Subject: [python-ideas] Briefer string format c s s t e x t +

f ' { n l } { s e l e c t o r } { s p a c e } { { { n l } ' I ' v e s e e n o t h e r s m a k e s i m i l a r s u g g e s t i o n s , b u t t o m y k n o w l e d g e t h e y d i d n ’ t i n c l u d e t h i s p l e a s i n g b r e v i t y a s p e c t . https://mail.python.org/pipermail/python-ideas/2015-July/034657.html @mariatta PYCON CANADA 2017 #PEPtalk

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Jul 20 01:12:31 CEST 2015 From: Eric V. Smith Subject: Re: [python-ideas] Briefer string format https://mail.python.org/pipermail/python-ideas/2015-July/034658.html Jul 20 01:27:42 CEST @mariatta PYCON CANADA 2017 #PEPtalk

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Jul 20 01:12:31 CEST 2015 W h a t w o u l d t h i s d o ? From: Eric V. Smith Subject: Re: [python-ideas] Briefer string format https://mail.python.org/pipermail/python-ideas/2015-July/034658.html Jul 20 01:27:42 CEST @mariatta PYCON CANADA 2017 #PEPtalk

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Jul 20 01:12:31 CEST 2015 From: C. A. Subject: Re: [python-ideas] Briefer string format https://mail.python.org/pipermail/python-ideas/2015-July/034660.html Jul 20 01:27:42 CEST Jul 20 01:44:09 CEST @mariatta PYCON CANADA 2017 #PEPtalk

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I ’ m

1 o n t h e s p e c ific i d e a , t h o u g h d efin i t e l y s y m p a t h e t i c t o t h e b r o a d e r c o n c e p t o f s i m p l ifie d f o r m a t t i n g o f s t r i n g s . Jul 20 01:12:31 CEST 2015 From: C. A. Subject: Re: [python-ideas] Briefer string format https://mail.python.org/pipermail/python-ideas/2015-July/034660.html Jul 20 01:27:42 CEST Jul 20 01:44:09 CEST @mariatta PYCON CANADA 2017 #PEPtalk

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Jul 20 01:12:31 CEST 2015 From: S. D. Subject: Re: [python-ideas] Briefer string format https://mail.python.org/pipermail/python-ideas/2015-July/034669.html Jul 20 01:27:42 CEST @mariatta PYCON CANADA 2017 #PEPtalk Jul 20 02:43:29 CEST Jul 20 01:44:09 CEST

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I t ’ s s y n t a c t i c s u g a r f o r a s i m p l e f u n c t i o n c a l l w i t h p e r f e c t l y w e l l d efin e d s e m a n t i c s

d o n ’ t e v e n h a v e t o m o d i f y t h e s t r i n g l i t e r a l . I ’ m + 1 . Jul 20 01:12:31 CEST 2015 From: S. D. Subject: Re: [python-ideas] Briefer string format https://mail.python.org/pipermail/python-ideas/2015-July/034669.html Jul 20 01:27:42 CEST @mariatta PYCON CANADA 2017 #PEPtalk Jul 20 02:43:29 CEST Jul 20 01:44:09 CEST

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that escalated quickly @mariatta PYCON CANADA 2017 #PEPtalk

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Jul 20 01:12:31 CEST 2015 From: Guido van Rossum Subject: Re: [python-ideas] Briefer string format https://mail.python.org/pipermail/python-ideas/2015-July/034729.html Jul 20 01:27:42 CEST Jul 20 01:44:09 CEST Jul 20 02:43:29 CEST Jul 21 08:05:15 CEST @mariatta PYCON CANADA 2017 #PEPtalk

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T h a n k s , E r i c ! Y o u ’ r e a d d r e s s i n g a l l m y c o n c e r n s a n d y o u ’ r e g o i n g e x a c t l y w h e r e I w a n t e d t h i s t o g o . I h o p e t h a t y o u w i l lfin d t h e t i m e t o w r i t e u p a P E P ; Jul 20 01:12:31 CEST 2015 From: Guido van Rossum Subject: Re: [python-ideas] Briefer string format https://mail.python.org/pipermail/python-ideas/2015-July/034729.html Jul 20 01:27:42 CEST Jul 20 01:44:09 CEST Jul 20 02:43:29 CEST Jul 21 08:05:15 CEST @mariatta PYCON CANADA 2017 #PEPtalk

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By: Eric V. Smith PEP 498: Literal String Formatting August 7th, 2015 @mariatta PYCON CANADA 2017 #PEPtalk

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By: Eric V. Smith PEP 498: Literal String Interpolation August 7th, 2015 August 30th, 2015 @mariatta PYCON CANADA 2017 #PEPtalk

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ready for pronouncement PEP 498: Literal String Interpolation 1 August 7th, 2015 August 30th, 2015 September 5th, 2015 @mariatta PYCON CANADA 2017 #PEPtalk

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PEP 498: Literal String Interpolation August 7th, 2015 August 30th, 2015 September 5th, 2015 September 7th, 2015 @mariatta PYCON CANADA 2017 #PEPtalk

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“The existing ways of formatting are either error prone , inflexible , or cumbersome .” RATIONALE @mariatta PYCON CANADA 2017 #PEPtalk

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name = "Bart"

print( "Hello, %s ." % name) Hello, Bart. @mariatta PYCON CANADA 2017 #PEPtalk

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name = "Bart"

age =

print( "Hello,

%s . You’re %s ."

% name, age ) Traceback (most recent call last):

File "<stdin>", line 1, in <module>

TypeError: not enough arguments for format string @mariatta PYCON CANADA 2017 #PEPtalk

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name = "Bart"

age = 10

print( "Hello, %s . You’re %s ." %

( name, age ) ) Hello, Bart. You're 10. @mariatta PYCON CANADA 2017 #PEPtalk

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PEP 3101: str.format https://www.python.org/dev/peps/pep-31 01 @mariatta PYCON CANADA 2017 #PEPtalk

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name = "Bart"

age = 10

print( "Hello,

{name} . You’re {age} . " .format( name =name, age =age)) Hello, Bart. You're 10.

@mariatta PYCON CANADA 2017 #PEPtalk

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PEP 498: f-string https://www.python.org/dev/peps/pep- 0498 @mariatta PYCON CANADA 2017 #PEPtalk

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name = "Bart"

age = 10

print( "Hello,

{name} . You’re {age} . " .format( name =name, age =age)) @mariatta PYCON CANADA 2017 #PEPtalk

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name = "Bart"

age = 10

print( "Hello,

{name} . You’re {age} . " ) @mariatta PYCON CANADA 2017 #PEPtalk

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name = "Bart"

age = 10

print( f "Hello, {name} . You’re

{age} ." ) @mariatta PYCON CANADA 2017 #PEPtalk

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name = "Bart"

age = 10

print( f "Hello, {name} . You’re

{age} ." ) @mariatta PYCON CANADA 2017 #PEPtalk Hello, Bart. You're 10.

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recap @mariatta PYCON CANADA 2017 #PEPtalk

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"Hello, %s . You’re %s . " % (name, age ) @mariatta PYCON CANADA 2017 #PEPtalk

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"Hello, %s . You’re %s . " % (name, age ) "Hello, {name} . You’re {age} ." .format( name= name, age= age) @mariatta PYCON CANADA 2017 #PEPtalk

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"Hello, %s . You’re %s . " % (name, age ) "Hello, {name} . You’re {age} ." .format( name= name, age= age) f " Hello, {name} . You’re {age} . "

@mariatta PYCON CANADA 2017 #PEPtalk

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f " Hello, {name} . You’re {age} . "

Expression @mariatta PYCON CANADA 2017 #PEPtalk

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f " Hello, {name} . You’re {age} . "

Literal @mariatta PYCON CANADA 2017 #PEPtalk

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f " Hello, world. "

f-string @mariatta PYCON CANADA 2017 #PEPtalk

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f "..."

✅ F' ...'

✅ f """..."""

✅ @mariatta PYCON CANADA 2017 #PEPtalk

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✅

r + f = fr " … " Raw f-strings @mariatta PYCON CANADA 2017 #PEPtalk

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print( "The smiley face emoji is \U0001f600" ) @mariatta PYCON CANADA 2017 #PEPtalk

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print( "The smiley face emoji is \U0001f600" ) The smiley face emoji is ( @mariatta PYCON CANADA 2017 #PEPtalk

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print( "The smiley face emoji is \U0001f600" ) The smiley face emoji is (

print( r "The smiley face unicode is \U0001f600" ) @mariatta PYCON CANADA 2017 #PEPtalk

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print( "The smiley face emoji is \U0001f600" ) The smiley face emoji is (

print( r "The smiley face unicode is \U0001f600" ) The smiley face unicode is \U0001f600 @mariatta PYCON CANADA 2017 #PEPtalk

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code = "emoji "

print( f"The smiley face {code} is \U0001f600" ) @mariatta PYCON CANADA 2017 #PEPtalk

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code = "emoji "

print( f"The smiley face {code} is \U0001f600" ) The smiley face emoji is ( @mariatta PYCON CANADA 2017 #PEPtalk

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code = "emoji "

print( f"The smiley face {code} is \U0001f600" ) The smiley face emoji is (

code = "unicode "

print( f r "The smiley face {code} is \U0001f600" ) @mariatta PYCON CANADA 2017 #PEPtalk

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code = "emoji "

print( f"The smiley face {code} is \U0001f600" ) The smiley face emoji is (

code = "unicode "

print( f r "The smiley face {code} is \U0001f600" ) The smiley face unicode is \U0001f600 @mariatta PYCON CANADA 2017 #PEPtalk

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rF """..."""

✅ fr "..."

✅ RF "..."

✅ PYCON CANADA 2017 @mariatta PYCON CANADA 2017 #PEPtalk

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fb "..."

❌ uf "..."

❌ @mariatta PYCON CANADA 2017 #PEPtalk

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name = "bart simpson"

print( f"Hi {name.upper()} !” ) Hi BART SIMPSON!

@mariatta PYCON CANADA 2017 #PEPtalk

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def how_many_tacos(people ): ... return people * 3

...

people = 5

print( f"Order {how_many_tacos(people)} tacos for meetup!" ) Order 15 tacos for meetup!

@mariatta PYCON CANADA 2017 #PEPtalk

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pi = 3.14159265

print( "pi 3 decimal places %.3f " % pi )

3.142

print( f"pi 3 decimal places {pi:.3f} " )

3.142

@mariatta PYCON CANADA 2017 #PEPtalk

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number =

1024

print( f"hex: {number:#0x} " )

hex: 0x400

print( f"binary: {number:#0b} " )

binary: 0b10000000000

print( f"octal: {number:#0o} " )

octal: 0o2000

@mariatta PYCON CANADA 2017 #PEPtalk

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pycon_ca = datetime ( year= 2017, month= 11, day= 19)

print( f" {pycon_ca:%b %d, %Y} " )

Nov 19, 2017

print( f" {name:>20} " )

            Bart

print( f" {age:=+5d} " )

@mariatta PYCON CANADA 2017 #PEPtalk

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❌

Not in Docstrings

def spam(): ...
f " doing stuff "

...

spam. doc is None True bpo-28739 @mariatta PYCON CANADA 2017 #PEPtalk

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Multi-line S trings? bpo-29668

name = "Bart"

prize = 50

tomorrow =

today() + timedelta( days= 1 )

message = ( f "Dear {name} ,"

... "You can win {prize:.2f} $"

... "Make a purchase before {tomorrow:%Y-%b-%d} " )

@mariatta PYCON CANADA 2017 #PEPtalk

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✅

Multi-line S trings

message = ( f "Dear {name} ,"

... f "You can win {prize:.2f} $"

... f "Make a purchase before {tomorrow}:%Y-%b-%d " )

@mariatta PYCON CANADA 2017 #PEPtalk bpo-29668

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IDLE Needs Syntax Highlighting bpo-29287 • Needs separate colorization to make the expression distinct from the rest of the string. • Needs close-brace matching. • Would be desirable to have autocompletion as well. @mariatta PYCON CANADA 2017 #PEPtalk

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Documentation … ? Python 3.6.2 @mariatta PYCON CANADA 2017 #PEPtalk

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Documentation … ?

Python 3.6.3 @mariatta PYCON CANADA 2017 #PEPtalk

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Documentation https://docs.python.org/3/reference/lexical_analysis.html#formatted-string-literals ⭐ / Formatted String Literal 0 docs.python.org

glossary > f-string @mariatta PYCON CANADA 2017 #PEPtalk

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⏱

timeit @mariatta PYCON CANADA 2017 #PEPtalk

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$ python3 -mtimeit -s 'a= 2 ' "'%s' % a " 10000000 loops, best of 3:

0.197

usec per loop @mariatta PYCON CANADA 2017 #PEPtalk

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$ python3 -mtimeit -s 'a=2' "'%s' % a" 10000000 loops, best of 3: 0.197

usec per loop $ python3 -mtimeit -s 'a=2' '"{}".format(a)' 1000000 loops, best of 3: 0.341

usec per loop @mariatta PYCON CANADA 2017 #PEPtalk

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$ python3 -mtimeit -s 'a=2' "'%s' % a" 10000000 loops, best of 3: 0.197

usec per loop $ python3 -mtimeit -s 'a=2' '"{}".format(a)' 1000000 loops, best of 3: 0.341

usec per loop $ python3 -mtimeit -s 'a=2' 'f" {a} "' 10000000 loops, best of 3: 0.105 usec per loop @mariatta PYCON CANADA 2017 #PEPtalk

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$ python3 -mtimeit -s 'a=2' "'%s' % a" 10000000 loops, best of 3:

0.197

usec per loop $ python3 -mtimeit -s 'a=2' '"{}".format(a)' 1000000 loops, best of 3: 0.341

usec per loop $ python3 -mtimeit -s 'a=2' ' f" {a} " ' 10000000 loops, best of 3:

0.105 usec per loop @mariatta PYCON CANADA 2017 #PEPtalk

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PEP 498 @mariatta PYCON CANADA 2017 #PEPtalk

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f-strings @mariatta PYCON CANADA 2017 #PEPtalk

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Python 3.6 download at www.python.org @mariatta PYCON CANADA 2017 #PEPtalk

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Python 3.6 download at www.python.org @mariatta PYCON CANADA 2017 #PEPtalk

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bonus! @mariatta PYCON CANADA 2017 #PEPtalk

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16 PEPs included @mariatta PYCON CANADA 2017 #PEPtalk

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16 PEPs included PEP 468

PEP 487

PEP 495

PEP 498 PEP 506

PEP 509

PEP 515

PEP 519 PEP 520

PEP 523

PEP 524

PEP 525 PEP 526

PEP 528

PEP 529

PEP 530 @mariatta PYCON CANADA 2017 #PEPtalk

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16 PEPs included PEP 468

PEP 487

PEP 495

PEP 498 PEP 506

PEP 509

PEP 515

PEP 519 PEP 520

PEP 523

PEP 524

PEP 525 PEP 526

PEP 528

PEP 529

PEP 530 @mariatta PYCON CANADA 2017 #PEPtalk

Slide 94

16 PEPs included PEP 468

PEP 487

PEP 495

PEP 498 PEP 506

PEP 509

PEP 515

PEP 519 PEP 520

PEP 523

PEP 524

PEP 525 PEP 526

PEP 528

PEP 529

PEP 530 @mariatta PYCON CANADA 2017 #PEPtalk 17

Slide 95

16 PEPs included PEP 468

PEP 487

PEP 495

PEP 498 PEP 506

PEP 509

PEP 515

PEP 519 PEP 520

PEP 523

PEP 524

PEP 525 PEP 526

PEP 528

PEP 529

PEP 530 @mariatta PYCON CANADA 2017 #PEPtalk 17 PEP 628 : add math.tau

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Thank you! file issues at bugs.python.org Mariatta Wijaya | mariatta@python.org

@mariatta PYCON CANADA 2017 #PEPtalk