Optimize textwrap.indent()

[methane]

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

[methane]

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%)

[hroncok]

This changes the exception type when bad type is passed:

Before:

>>> import textwrap
>>> textwrap.dedent(5)
Traceback (most recent call last):
 File "<python-input-1>", line 1, in <module>
 textwrap.dedent(5)
 ~~~~~~~~~~~~~~~^^^
 File "/usr/lib64/python3.14/textwrap.py", line 435, in dedent
 text = _whitespace_only_re.sub('', text)
TypeError: expected string or bytes-like object, got 'int'

After:

>>> import textwrap
>>> textwrap.dedent(5)
Traceback (most recent call last):
 File "<python-input-1>", line 1, in <module>
 textwrap.dedent(5)
 ~~~~~~~~~~~~~~~^^^
 File "/usr/lib64/python3.14/textwrap.py", line 432, in dedent
 lines = text.split('\n')
 ^^^^^^^^^^
AttributeError: 'int' object has no attribute 'split'

The exception context itself could be better in both cases, but arguably, TypeError is better here. This breaks tests assumption in https://github.com/laurent-laporte-pro/deprecated/blob/3f67ca71143479ef7ce71786538b2bc0ef9ee4b4/tests/test_deprecated.py#L201

[methane]

@hroncok This issue is about indent, not dedent.

See #131919 instead.

[hroncok]

#131919 references this issue.