133 lines
4.7 KiB
Python
133 lines
4.7 KiB
Python
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import re as _re
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from collections import ChainMap as _ChainMap
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class _TemplateMetaclass(type):
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pattern = r"""
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%(delim)s(?:
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(?P<escaped>%(delim)s) | # Escape sequence of two delimiters
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(?P<named>%(id)s) | # delimiter and a Python identifier
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{(?P<braced>%(id)s)} | # delimiter and a braced identifier
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(?P<invalid>) # Other ill-formed delimiter exprs
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)
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"""
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def __init__(cls, name, bases, dct):
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super(_TemplateMetaclass, cls).__init__(name, bases, dct)
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if 'pattern' in dct:
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pattern = cls.pattern
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else:
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pattern = _TemplateMetaclass.pattern % {
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'delim' : _re.escape(cls.delimiter),
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'id' : cls.idpattern,
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}
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cls.pattern = _re.compile(pattern, cls.flags | _re.VERBOSE)
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class Template(metaclass=_TemplateMetaclass):
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"""A string class for supporting $-substitutions."""
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delimiter = '$'
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idpattern = r'[_a-z][_a-z0-9]*'
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flags = _re.IGNORECASE
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def __init__(self, template):
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self.template = template
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# Search for $$, $identifier, ${identifier}, and any bare $'s
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def _invalid(self, mo):
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i = mo.start('invalid')
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lines = self.template[:i].splitlines(keepends=True)
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if not lines:
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colno = 1
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lineno = 1
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else:
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colno = i - len(''.join(lines[:-1]))
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lineno = len(lines)
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raise ValueError('Invalid placeholder in string: line %d, col %d' %
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(lineno, colno))
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def substitute(*args, **kws):
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if not args:
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raise TypeError("descriptor 'substitute' of 'Template' object "
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"needs an argument")
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self, *args = args # allow the "self" keyword be passed
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if len(args) > 1:
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raise TypeError('Too many positional arguments')
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if not args:
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mapping = kws
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elif kws:
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mapping = _ChainMap(kws, args[0])
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else:
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mapping = args[0]
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# Helper function for .sub()
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def convert(mo):
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# Check the most common path first.
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named = mo.group('named') or mo.group('braced')
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if named is not None:
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return str(mapping.get(named,''))
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if mo.group('escaped') is not None:
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return self.delimiter
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if mo.group('invalid') is not None:
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self._invalid(mo)
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raise ValueError('Unrecognized named group in pattern',
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self.pattern)
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return self.pattern.sub(convert, self.template)
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def strict_substitute(*args, **kws):
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if not args:
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raise TypeError("descriptor 'substitute' of 'Template' object "
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"needs an argument")
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self, *args = args # allow the "self" keyword be passed
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if len(args) > 1:
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raise TypeError('Too many positional arguments')
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if not args:
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mapping = kws
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elif kws:
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mapping = _ChainMap(kws, args[0])
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else:
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mapping = args[0]
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# Helper function for .sub()
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def convert(mo):
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# Check the most common path first.
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named = mo.group('named') or mo.group('braced')
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if named is not None:
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return str(mapping[named])
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if mo.group('escaped') is not None:
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return self.delimiter
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if mo.group('invalid') is not None:
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self._invalid(mo)
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raise ValueError('Unrecognized named group in pattern',
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self.pattern)
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return self.pattern.sub(convert, self.template)
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def safe_substitute(*args, **kws):
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if not args:
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raise TypeError("descriptor 'safe_substitute' of 'Template' object "
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"needs an argument")
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self, *args = args # allow the "self" keyword be passed
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if len(args) > 1:
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raise TypeError('Too many positional arguments')
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if not args:
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mapping = kws
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elif kws:
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mapping = _ChainMap(kws, args[0])
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else:
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mapping = args[0]
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# Helper function for .sub()
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def convert(mo):
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named = mo.group('named') or mo.group('braced')
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if named is not None:
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try:
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return str(mapping[named])
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except KeyError:
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return mo.group()
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if mo.group('escaped') is not None:
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return self.delimiter
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if mo.group('invalid') is not None:
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return mo.group()
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raise ValueError('Unrecognized named group in pattern',
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self.pattern)
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return self.pattern.sub(convert, self.template)
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