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max( str ) should be fast with PEP 393 #59431

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vpython mannequin opened this issue Jun 29, 2012 · 3 comments
Closed

max( str ) should be fast with PEP 393 #59431

vpython mannequin opened this issue Jun 29, 2012 · 3 comments
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interpreter-core (Objects, Python, Grammar, and Parser dirs) type-feature A feature request or enhancement

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@vpython
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Mannequin

vpython mannequin commented Jun 29, 2012

BPO 15226
Nosy @loewis, @vstinner

Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

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GitHub fields:

assignee = None
closed_at = <Date 2012-06-30.10:12:06.635>
created_at = <Date 2012-06-29.19:53:25.041>
labels = ['interpreter-core', 'type-feature', 'invalid']
title = 'max( str ) should be fast with PEP 393'
updated_at = <Date 2012-06-30.10:12:06.634>
user = 'https://bugs.python.org/vpython'

bugs.python.org fields:

activity = <Date 2012-06-30.10:12:06.634>
actor = 'loewis'
assignee = 'none'
closed = True
closed_date = <Date 2012-06-30.10:12:06.635>
closer = 'loewis'
components = ['Interpreter Core']
creation = <Date 2012-06-29.19:53:25.041>
creator = 'v+python'
dependencies = []
files = []
hgrepos = []
issue_num = 15226
keywords = []
message_count = 3.0
messages = ['164351', '164352', '164362']
nosy_count = 3.0
nosy_names = ['loewis', 'vstinner', 'v+python']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = None
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue15226'
versions = ['Python 3.3']
@vpython
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vpython mannequin commented Jun 29, 2012

This is stupid code, but it should be faster with PEP-393 than before, should it not?

str = ' ' * 5000000 + "this is really a string example....wow!!!";
for ix in range( 9000 ):
z = max(str)
print("Max character: " + max(str))

While the new C API seems to support quickly finding the max character in a string, Python code does not benefit.

@vpython vpython mannequin added the interpreter-core (Objects, Python, Grammar, and Parser dirs) label Jun 29, 2012
@loewis
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loewis mannequin commented Jun 29, 2012

What the C code finds quickly (in constant time) is that the maximum is <=127. Most code doesn't know (and doesn't care) what the actual maximum is. So I see no bug here.

@vpython
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vpython mannequin commented Jun 29, 2012

Ah, so then it would require a new API to make the Python code as smart as the C code, max is too general.

bpo-15016 is an example of Python code that could benefit from knowing in constant time if the string contained only characters < 128, or if the string contained only characters < 256... a three way decision.

@vpython vpython mannequin added the type-feature A feature request or enhancement label Jun 29, 2012
@loewis loewis mannequin closed this as completed Jun 30, 2012
@loewis loewis mannequin added the invalid label Jun 30, 2012
@ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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