Sep 9, 2023 · Sep 21, 2023 · Sep 22, 2023 · Sep 23, 2023 · Sep 22, 2023 · Sep 23, 2023
diff --git a/Lib/csv.py b/Lib/csv.py

        # if we see an extra quote between delimiters, we've got a
        # double quoted format
        # in future Python versions this zero width look-ahead assert can be replaced with atomic groups
        dq_regexp = re.compile(
                               r"((%(delim)s)|^)\W*%(quote)s[^%(delim)s\n]*%(quote)s[^%(delim)s\n]*%(quote)s\W*((%(delim)s)|$)" % \
                               r"((%(delim)s)|^)\W*%(quote)s(?=(?P<zero>[^%(delim)s%(quote)s\n]*))(?P=zero)%(quote)s[^%(delim)s\n]*%(quote)s\W*((%(delim)s)|$)" % \
                               {'delim':re.escape(delim), 'quote':quotechar}, re.MULTILINE)
Original file line number	Diff line number	Diff line change
Expand Up		@@ -270,8 +270,9 @@ def _guess_quote_and_delimiter(self, data, delimiters):

		# if we see an extra quote between delimiters, we've got a
		# double quoted format
		# in future Python versions this zero width look-ahead assert can be replaced with atomic groups
Copy link Member AA-TurnerSep 22, 2023 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. Please may you explain this comment? Copy link Author sg3-141-592Sep 23, 2023 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. Sure, this zero-width lookahead assertion change in the Regex can be done with an atomic group which is cleaner and more concise. `# Current change(,\|^)\W"(?=(?P<zero>[^,\|"\n]))(?P=zero)"[^,\|\n]"\W(,\|$)# Atomic Group(,\|^)\W"(?>[^,\|"\n])"[^,\|\n]"\W(,\|$)` But atomic groups are only supported in Python 3.11 onwards so I avoided using them here. Copy link Member AA-TurnerSep 23, 2023 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. Thanks Sean. This PR (if merged) would be part of Python 3.13, so let's use the better atomic group method. A Copy link Author sg3-141-592Sep 23, 2023 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. Sure, I've switched us to the simpler atomic group setup. Performance is identical to the previous fix.
		dq_regexp = re.compile(
		r"((%(delim)s)\|^)\W%(quote)s[^%(delim)s\n]%(quote)s[^%(delim)s\n]%(quote)s\W((%(delim)s)\|$)" % \
		r"((%(delim)s)\|^)\W%(quote)s(?=(?P<zero>[^%(delim)s%(quote)s\n]))(?P=zero)%(quote)s[^%(delim)s\n]%(quote)s\W((%(delim)s)\|$)" % \
		{'delim':re.escape(delim), 'quote':quotechar}, re.MULTILINE)


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