学习python的string模块（二）

    >>> values={'stu1':'tom','stu2':'selina','stu3':'harry'}
    >>> t=string.Template("i'm $stu1n;$stu2 have $$100")
    >>> t.substitute(values)
    "i'm tomn;selina have $100"

    [root@station1 ~]# vim mytemplate.py
    #!/usr/bin/python
    import string
    class Mytemplate(string.Template):
            delimiter = "%"
            idpattern = "_[a-z]+"

    s = '''delimiter is %%
            replaced : %_stu
            no replaced : %stu
    '''
    values = {"_stu":"tom","stu":"selina"}
    t=Mytemplate(s)
    print '%s' % t.safe_substitute(values)

    [root@station1 ~]# python mytemplate.py
    delimiter is %
    replaced : tom
    no replaced : %stu

    import re as _re

    class _multimap:
        """Helper class for combining multiple mappings.

        Used by .{safe_,}substitute() to combine the mapping and keyword
        arguments.
        """
        def __init__(self, primary, secondary):
            self._primary = primary
            self._secondary = secondary

        def __getitem__(self, key):
            try:
                return self._primary[key]
            except KeyError:
                return self._secondary[key]

    class _TemplateMetaclass(type):
        pattern = r"""
        %(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):
            super(_TemplateMetaclass, cls).__init__(name, bases, dct)
            if 'pattern' in dct:
                pattern = cls.pattern
            else:
                pattern = _TemplateMetaclass.pattern % {
                    'delim' : _re.escape(cls.delimiter),
                    'id' : cls.idpattern,
                    }
            cls.pattern = _re.compile(pattern, _re.IGNORECASE | _re.VERBOSE)

    class Template:
        """A string class for supporting $-substitutions."""
        __metaclass__ = _TemplateMetaclass

        delimiter = '$'
        idpattern = r'[_a-z][_a-z0-9]*'

        def __init__(self, template):
            self.template = template

        # Search for $$, $identifier, ${identifier}, and any bare $'s

        def _invalid(self, mo):
            i = mo.start('invalid')
            lines = self.template[:i].splitlines(True)
            if not lines:
                colno = 1
                lineno = 1
            else:
                colno = i - len(''.join(lines[:-1]))
                lineno = len(lines)
            raise ValueError('Invalid placeholder in string: line %d, col %d' %
                             (lineno, colno))

        def substitute(self, *args, **kws):
            if len(args) > 1:
                raise TypeError('Too many positional arguments')
            if not args:
                mapping = kws
            elif kws:
                mapping = _multimap(kws, args[0])
            else:
                mapping = args[0]
            # Helper function for .sub()
            def convert(mo):
                # Check the most common path first.
                named = mo.group('named') or mo.group('braced')
                if named is not None:
                    val = mapping[named]
                    # We use this idiom instead of str() because the latter will
                    # fail if val is a Unicode containing non-ASCII characters.
                    return '%s' % (val,)
                if mo.group('escaped') is not None:
                    return self.delimiter
                if mo.group('invalid') is not None:
                    self._invalid(mo)
                raise ValueError('Unrecognized named group in pattern',
                                 self.pattern)
            return self.pattern.sub(convert, self.template)

        def safe_substitute(self, *args, **kws):
            if len(args) > 1:
                raise TypeError('Too many positional arguments')
            if not args:
                mapping = kws
            elif kws:
                mapping = _multimap(kws, args[0])
            else:
                mapping = args[0]
            # Helper function for .sub()
            def convert(mo):
                named = mo.group('named')
                if named is not None:
                    try:
                        # We use this idiom instead of str() because the latter
                        # will fail if val is a Unicode containing non-ASCII
                        return '%s' % (mapping[named],)
                    except KeyError:
                        return self.delimiter + named
                braced = mo.group('braced')
                if braced is not None:
                    try:
                        return '%s' % (mapping[braced],)
                    except KeyError:
                        return self.delimiter + '{' + braced + '}'
                if mo.group('escaped') is not None:
                    return self.delimiter
                if mo.group('invalid') is not None:
                    return self.delimiter
                raise ValueError('Unrecognized named group in pattern