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gh-119123: Fix sniffer to understand csv lists #134219

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gh-119123: Fix sniffer to understand csv lists #134219

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e6f9e16
gh-119123: Fix sniffer to understand csv lists
aterrel May 19, 2025
fa30a9d
Merge branch 'main' into gh-119123
aterrel May 19, 2025
cbbcf1c
gh-119123: adds test for failing csv lists
aterrel May 19, 2025
4fd787f
Merge remote-tracking branch 'origin/gh-119123' into gh-119123
aterrel May 19, 2025
eef30e6
fix whitespace issues
aterrel May 19, 2025
2921167
Merge branch 'main' into gh-119123
aterrel May 19, 2025
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3 changes: 3 additions & 0 deletions Lib/csv.py
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Original file line number Diff line number Diff line change
Expand Up @@ -282,6 +282,9 @@ def _guess_quote_and_delimiter(self, data, delimiters):
"""
import re

# Remove lists from the data, see issue 119123
data = re.sub(r'\[.*?\]', '', data)

matches = []
for restr in (r'(?P<delim>[^\w\n"\'])(?P<space> ?)(?P<quote>["\']).*?(?P=quote)(?P=delim)', # ,".*?",
r'(?:^|\n)(?P<quote>["\']).*?(?P=quote)(?P<delim>[^\w\n"\'])(?P<space> ?)', # ".*?",
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11 changes: 11 additions & 0 deletions Lib/test/test_csv.py
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Expand Up @@ -1331,11 +1331,22 @@ class TestSniffer(unittest.TestCase):
ghi\0jkl
"""

sample15 = dedent("""\
id;field1;group;sub_group
1;False;['345'];['10']
2;False;['112', '112'];['765', '766']
""")

def test_issue43625(self):
sniffer = csv.Sniffer()
self.assertTrue(sniffer.has_header(self.sample12))
self.assertFalse(sniffer.has_header(self.sample13))

def test_issue119123(self):
sniffer = csv.Sniffer()
dialect = sniffer.sniff(self.sample15, ",;")
self.assertEqual(dialect.delimiter, ';')

def test_has_header_strings(self):
"More to document existing (unexpected?) behavior than anything else."
sniffer = csv.Sniffer()
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