[Python-checkins] bpo-1198569: Allow string.Template braced pattern to be different (#3288)
Barry Warsaw
webhook-mailer at python.org
Mon Sep 4 16:32:13 EDT 2017
https://github.com/python/cpython/commit/ba4279683f8eb8f59be10d12547ea89480614388
commit: ba4279683f8eb8f59be10d12547ea89480614388
branch: master
author: Barry Warsaw <barry at python.org>
committer: GitHub <noreply at github.com>
date: 2017-09-04T16:32:10-04:00
summary:
bpo-1198569: Allow string.Template braced pattern to be different (#3288)
* bpo-1198569: Allow the braced pattern to be different
``string.Template`` subclasses can optionally define ``braceidpattern`` if
they want to specify different placeholder patterns inside and outside the
braces. If None (the default) it falls back to ``idpattern``.
files:
A Misc/NEWS.d/next/Library/2017-09-04-10-53-06.bpo-1198569.vhh2nY.rst
M Doc/library/string.rst
M Lib/string.py
M Lib/test/test_string.py
diff --git a/Doc/library/string.rst b/Doc/library/string.rst
index 8176a81d4cf..1a9b6309752 100644
--- a/Doc/library/string.rst
+++ b/Doc/library/string.rst
@@ -754,9 +754,21 @@ attributes:
be set in the subclass's class namespace).
* *idpattern* -- This is the regular expression describing the pattern for
- non-braced placeholders (the braces will be added automatically as
- appropriate). The default value is the regular expression
- ``[_a-z][_a-z0-9]*``.
+ non-braced placeholders. The default value is the regular expression
+ ``[_a-z][_a-z0-9]*``. If this is given and *braceidpattern* is ``None``
+ this pattern will also apply to braced placeholders.
+
+ .. versionchanged:: 3.7
+ *braceidpattern* can be used to define separate patterns used inside and
+ outside the braces.
+
+* *braceidpattern* -- This is like *idpattern* but describes the pattern for
+ braced placeholders. Defaults to ``None`` which means to fall back to
+ *idpattern* (i.e. the same pattern is used both inside and outside braces).
+ If given, this allows you to define different patterns for braced and
+ unbraced placeholders.
+
+ .. versionadded:: 3.7
* *flags* -- The regular expression flags that will be applied when compiling
the regular expression used for recognizing substitutions. The default value
diff --git a/Lib/string.py b/Lib/string.py
index bc9508c1e6e..b46e60c38f4 100644
--- a/Lib/string.py
+++ b/Lib/string.py
@@ -57,7 +57,7 @@ class _TemplateMetaclass(type):
%(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<braced>%(bid)s)} | # delimiter and a braced identifier
(?P<invalid>) # Other ill-formed delimiter exprs
)
"""
@@ -70,6 +70,7 @@ def __init__(cls, name, bases, dct):
pattern = _TemplateMetaclass.pattern % {
'delim' : _re.escape(cls.delimiter),
'id' : cls.idpattern,
+ 'bid' : cls.braceidpattern or cls.idpattern,
}
cls.pattern = _re.compile(pattern, cls.flags | _re.VERBOSE)
@@ -79,6 +80,7 @@ class Template(metaclass=_TemplateMetaclass):
delimiter = '$'
idpattern = r'[_a-z][_a-z0-9]*'
+ braceidpattern = None
flags = _re.IGNORECASE
def __init__(self, template):
diff --git a/Lib/test/test_string.py b/Lib/test/test_string.py
index a7b8aad8aba..6e241ac72ab 100644
--- a/Lib/test/test_string.py
+++ b/Lib/test/test_string.py
@@ -282,6 +282,30 @@ class PathPattern(Template):
s = PathPattern('$bag.foo.who likes to eat a bag of $bag.what')
self.assertEqual(s.substitute(m), 'tim likes to eat a bag of ham')
+ def test_idpattern_override_inside_outside(self):
+ # bpo-1198569: Allow the regexp inside and outside braces to be
+ # different when deriving from Template.
+ class MyPattern(Template):
+ idpattern = r'[a-z]+'
+ braceidpattern = r'[A-Z]+'
+ flags = 0
+ m = dict(foo='foo', BAR='BAR')
+ s = MyPattern('$foo ${BAR}')
+ self.assertEqual(s.substitute(m), 'foo BAR')
+
+ def test_idpattern_override_inside_outside_invalid_unbraced(self):
+ # bpo-1198569: Allow the regexp inside and outside braces to be
+ # different when deriving from Template.
+ class MyPattern(Template):
+ idpattern = r'[a-z]+'
+ braceidpattern = r'[A-Z]+'
+ flags = 0
+ m = dict(foo='foo', BAR='BAR')
+ s = MyPattern('$FOO')
+ self.assertRaises(ValueError, s.substitute, m)
+ s = MyPattern('${bar}')
+ self.assertRaises(ValueError, s.substitute, m)
+
def test_pattern_override(self):
class MyPattern(Template):
pattern = r"""
diff --git a/Misc/NEWS.d/next/Library/2017-09-04-10-53-06.bpo-1198569.vhh2nY.rst b/Misc/NEWS.d/next/Library/2017-09-04-10-53-06.bpo-1198569.vhh2nY.rst
new file mode 100644
index 00000000000..86754191e7d
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2017-09-04-10-53-06.bpo-1198569.vhh2nY.rst
@@ -0,0 +1,3 @@
+``string.Template`` subclasses can optionally define ``braceidpattern`` if
+they want to specify different placeholder patterns inside and outside the
+braces. If None (the default) it falls back to ``idpattern``.
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