[issue32912] Raise non-silent warning for invalid escape sequences
Serhiy Storchaka
report at bugs.python.org
Fri Jun 14 02:20:31 EDT 2019
Serhiy Storchaka <storchaka+cpython at gmail.com> added the comment:
In the particular case of pyparsing there was a bug in the docstring.
def sub(self, repl):
"""
Return Regex with an attached parse action to transform the parsed
result as if called using `re.sub(expr, repl, string) <https://docs.python.org/3/library/re.html#re.sub>`_.
Example::
make_html = Regex(r"(\w+):(.*?):").sub(r"<\1>\2</\1>")
print(make_html.transformString("h1:main title:"))
# prints "<h1>main title</h1>"
"""
\1 and \2 were interpreted as control characters U+0001 and U+0002, so the user could see
make_html = Regex(r"(\w+):(.*?):").sub(r"<^A>^B</^A>")
or
make_html = Regex(r"(\w+):(.*?):").sub(r"<☺>☻</☺>")
or
make_html = Regex(r"(\w+):(.*?):").sub(r"<></>")
depending on the output device.
So this examples proves the usefulness of the new warning.
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