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"""

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    Generating HTML tags

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"""

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from cgi import escape

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def tag_attr (name, value) :

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    return u'%s="%s"' % (name.rstrip('_'), escape(value, True))

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def tag_subcontent (subcontent) :

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    if not subcontent :

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        # skip

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        return

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    elif not isinstance(subcontent, basestring) and hasattr(subcontent, '__iter__') :

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        # render each sub-item recursively

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        for sc in subcontent :

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            for line in tag_subcontent(sc) :

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                yield line

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    else :

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        yield subcontent

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def tag_content (content) :

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    if not content:

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        # no output

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        return

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    elif isinstance(content, basestring) :

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        # escape raw vlues

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        yield escape(unicode(content))

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    else :

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        # treat it as subcontent

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        for line in tag_subcontent(content) :

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            yield line

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def tag (name, *content, **attrs) :

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    attr_stuff = " " + " ".join(tag_attr(n, v) for n, v in attrs.iteritems()) if attrs else ""

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    if content and all(content) :

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        # tag with content

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        yield u"<%s%s>" % (name, attr_stuff)

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        for c in content :

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            for line in tag_content(c) :

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                yield u"\t" + line

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        yield u"</%s>" % (name, )

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    else :

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        # singleton tag

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        yield u"<%s%s />" % (name, attr_stuff)

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def raw (data) :

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    yield data

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class TagFactory (object) :

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    def __getattr__ (self, name) :

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        def build_tag (*content, **attrs) :

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            return tag(name, *content, **attrs)

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        return build_tag

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tags = TagFactory()

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def render_lines (tags, charset=None) :

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    for line in tag_content(tags) :

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        if charset :

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            yield line.encode(charset)

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        else :

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            yield line

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def render (tags, charset=None) :

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    data = u'\n'.join(render_lines(tags))

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    if charset :

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        return data.encode(charset)

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    else :

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        return data

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def render_out (tags, out, charset='utf-8') :

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    """

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        Write the rendered tags into the given output stream using the given encoding

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    """

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    for line in render_lines(tags, charset) :

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        out.write(line + '\n')

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