Description

methane

opened on Jul 28, 2023

Issue body actions

Current code:

def indent(text, prefix, predicate=None):
    """Adds 'prefix' to the beginning of selected lines in 'text'.

    If 'predicate' is provided, 'prefix' will only be added to the lines
    where 'predicate(line)' is True. If 'predicate' is not provided,
    it will default to adding 'prefix' to all non-empty lines that do not
    consist solely of whitespace characters.
    """
    if predicate is None:
        def predicate(line):
            return line.strip()

    def prefixed_lines():
        for line in text.splitlines(True):
            yield (prefix + line if predicate(line) else line)
    return ''.join(prefixed_lines())

• predicate = str.strip is faster than def predicate(line)
• ''.join(x) converts input iterable to sequence. Using generator just makes overhead.
• creating temporary prefix + line is avoidable.

Linked PRs

• gh-107369: optimize textwrap.indent() #107374
• gh-107369: Optimise textwrap.indent() #131923

Reacted by Goto Hayato

Activity

1. methane

   added

   type-featureA feature request or enhancementA feature request or enhancement

   performancePerformance or resource usagePerformance or resource usage

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   and removed

   type-featureA feature request or enhancementA feature request or enhancement

   on Jul 28, 2023
2. methane commented on Jul 28, 2023

   

   methane

   on Jul 28, 2023

   MemberAuthor

   More actions

   import timeit
   import textwrap
   
   with open("Objects/unicodeobject.c") as f:
       text = f.read()
   
   it = timeit.Timer(lambda: textwrap.indent(text, " "*4))
   result = it.repeat(number=1000)
   result.sort()
   print(f"indent {len(text.splitlines())} lines.")
   print(f"{result[0]:.4f}msec")

   before: 2.8msec
   after: 2.1msec (-25%)
3. methane

   added a commit that references this issue on Jul 29, 2023

   gh-107369: optimize textwrap.indent() (#107374)

   37551c9
4. sunmy2019

   closed this as completedon Jul 29, 2023
5. AA-Turner

   added a commit that references this issue on Mar 31, 2025

   gh-107369: Optimise ``textwrap.indent()`` (#131923)

   51e0f2b
6. hroncok commented on Apr 14, 2025

   

   hroncok

   on Apr 14, 2025 · Hidden as off-topic

   show commentMore actions
7. methane commented on Apr 15, 2025

   

   methane

   on Apr 15, 2025

   MemberAuthor

   More actions

   @hroncok This issue is about indent, not dedent.

   See #131919 instead.
8. hroncok commented on Apr 15, 2025

   

   hroncok

   on Apr 15, 2025 · Hidden as resolved

   show commentMore actions
9. hroncok commented on Apr 15, 2025

   

   hroncok

   on Apr 15, 2025

   Contributor

   More actions

   Moved to #131919 (comment)
10. methane commented on Apr 15, 2025

    

    methane

    on Apr 15, 2025

    MemberAuthor

    More actions

    #131919 references this issue.

    It references #130167, not this issue.

    #131923 references this issue because it makes textwrap.indent faster again. It is unrelated to textwrap.dedent.

    Reacted by Miro Hrončok
11. hroncok commented on Apr 15, 2025

    

    hroncok

    on Apr 15, 2025

    Contributor

    More actions

    Sorry for my confusion.

Issue actions