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gh-140627: Fix textwrap.wrap removing whitespace at start of paragraph #140639

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gh-140627: Fix textwrap.wrap removing whitespace at start of paragraph #140639

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2 changes: 2 additions & 0 deletions Lib/test/test_textwrap.py
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Original file line number Diff line number Diff line change
Expand Up @@ -388,6 +388,8 @@ def test_drop_whitespace_leading_whitespace(self):
[" This is a sentence with leading whitespace."])
self.check_wrap(text, 30,
[" This is a sentence with", "leading whitespace."])
self.check_wrap(' ABCDEFG', 1,
[' ', 'A', 'B', 'C', 'D', 'E', 'F', 'G'])
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Maybe add other cases

>>> textwrap.wrap('   ABCDEFG', width=1)
[' ', 'A', 'B', 'C', 'D', 'E', 'F', 'G']
>>> textwrap.wrap('   ABCDEFG', width=2)
[' A', 'BC', 'DE', 'FG']
>>> textwrap.wrap('   ABCDEFG', width=3)
['   ', 'ABC', 'DEF', 'G']


def test_drop_whitespace_whitespace_line(self):
# Check that drop_whitespace skips the whole line if a non-leading
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8 changes: 6 additions & 2 deletions Lib/textwrap.py
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Original file line number Diff line number Diff line change
Expand Up @@ -304,8 +304,12 @@ def _wrap_chunks(self, chunks):

# If the last chunk on this line is all whitespace, drop it.
if self.drop_whitespace and cur_line and cur_line[-1].strip() == '':
cur_len -= len(cur_line[-1])
del cur_line[-1]
# If this is the first line keep it if a non-whitespace chunk follows
if not lines and len(cur_line) == 1 and chunks and chunks[-1].strip() != '':
pass
else:
cur_len -= len(cur_line[-1])
del cur_line[-1]
Comment on lines +307 to +312
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Suggested change
# If this is the first line keep it if a non-whitespace chunk follows
if not lines and len(cur_line) == 1 and chunks and chunks[-1].strip() != '':
pass
else:
cur_len -= len(cur_line[-1])
del cur_line[-1]
# Keep first non-whitespace chunk on the first line
if not (not lines and len(cur_line) == 1 and chunks and chunks[-1].strip()):
cur_len -= len(cur_line[-1])
del cur_line[-1]

Maybe this is better?

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Or

                if lines or len(cur_line) != 1 or not chunks or not chunks[-1].strip():
                    cur_len -= len(cur_line[-1])
                    del cur_line[-1]


if cur_line:
if (self.max_lines is None or
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2025-10-26-16-11-45.gh-issue-140627.BiEgy_.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Fix :func:`textwrap.wrap` to preserve a whitespace only line at the start of
a paragraph when non-whitespace text follows.
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