[3.7] bpo-28450: Fix and improve the documentation for unknown escapes in RE. (GH-11920). by serhiy-storchaka · Pull Request #12029 · python/cpython
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@@ -570,7 +570,8 @@ accepted by the regular expression parser::
only inside character classes.)
``'\u'`` and ``'\U'`` escape sequences are only recognized in Unicode patterns. In bytes patterns they are errors. patterns. In bytes patterns they are errors. Unknown escapes of ASCII letters are reserved for future use and treated as errors.
Octal escapes are included in a limited form. If the first digit is a 0, or if there are three octal digits, it is considered an octal escape. Otherwise, it is Expand Down Expand Up @@ -844,7 +845,9 @@ form. *string* is returned unchanged. *repl* can be a string or a function; if it is a string, any backslash escapes in it are processed. That is, ``\n`` is converted to a single newline character, ``\r`` is converted to a carriage return, and so forth. Unknown escapes such as ``\&`` are left alone. Backreferences, such so forth. Unknown escapes of ASCII letters are reserved for future use and treated as errors. Other unknown escapes such as ``\&`` are left alone. Backreferences, such as ``\6``, are replaced with the substring matched by group 6 in the pattern. For example::
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``'\u'`` and ``'\U'`` escape sequences are only recognized in Unicode patterns. In bytes patterns they are errors. patterns. In bytes patterns they are errors. Unknown escapes of ASCII letters are reserved for future use and treated as errors.
Octal escapes are included in a limited form. If the first digit is a 0, or if there are three octal digits, it is considered an octal escape. Otherwise, it is Expand Down Expand Up @@ -844,7 +845,9 @@ form. *string* is returned unchanged. *repl* can be a string or a function; if it is a string, any backslash escapes in it are processed. That is, ``\n`` is converted to a single newline character, ``\r`` is converted to a carriage return, and so forth. Unknown escapes such as ``\&`` are left alone. Backreferences, such so forth. Unknown escapes of ASCII letters are reserved for future use and treated as errors. Other unknown escapes such as ``\&`` are left alone. Backreferences, such as ``\6``, are replaced with the substring matched by group 6 in the pattern. For example::
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