Optimize textwrap.indent()

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

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%)

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

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

@hroncok

@hroncok This issue is about indent, not dedent.

See #131919 instead.

Moved to #131919 (comment)

#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.

Sorry for my confusion.

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Optimize textwrap.indent() #107369

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Optimize textwrap.indent() #107369

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methane commented on Jul 28, 2023

hroncok commented on Apr 14, 2025

methane commented on Apr 15, 2025

hroncok commented on Apr 15, 2025

hroncok commented on Apr 15, 2025

methane commented on Apr 15, 2025

hroncok commented on Apr 15, 2025

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