Make the regex pattern easier to read, understand, and modify
by factoring out the common prefix (the delimiter).
diff --git a/Lib/string.py b/Lib/string.py
index 623eb0e..7371c91 100644
--- a/Lib/string.py
+++ b/Lib/string.py
@@ -101,10 +101,12 @@
class _TemplateMetaclass(type):
pattern = r"""
- (?P<escaped>%(delim)s{2}) | # Escape sequence of two delimiters
- %(delim)s(?P<named>%(id)s) | # delimiter and a Python identifier
- %(delim)s{(?P<braced>%(id)s)} | # delimiter and a braced identifier
- (?P<invalid>%(delim)s) # Other ill-formed delimiter exprs
+ %(delim)s(?:
+ (?P<escaped>%(delim)s) | # Escape sequence of two delimiters
+ (?P<named>%(id)s) | # delimiter and a Python identifier
+ {(?P<braced>%(id)s)} | # delimiter and a braced identifier
+ (?P<invalid>) # Other ill-formed delimiter exprs
+ )
"""
def __init__(cls, name, bases, dct):