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copied!<p>@mattbasta has the right idea here. However, I want to propose something a bit different: implement <code>to_string</code> using <code>cElementTree.TreeBuilder</code>. I don't know if the super-fast serialization of ElementTree will win out against overhead of creating an ElementTree.</p> <p>Here is a wonky <code>TAG</code> class with a <code>to_string_b()</code> method that makes use of some micro-optimizations and uses a TreeBuilder to build the tree. (A possibly-important difference between your <code>to_string()</code> and TreeBuilder is that TreeBuilder will always escape output for XML, whereas yours will not.)</p> <pre><code>import xml.etree.cElementTree as ET class TAG(object): def __init__(self, tag="TAG", contents=None, **attributes): self.tag = tag # this is to insure that `contents` always has a uniform # type. if contents is None: self.contents = [] else: if isinstance(contents, basestring): # I suspect the calling code passes in a string as contents # in the common case, so this means that each character of # the string will be yielded one-by-one. let's avoid that by # wrapping in a list. self.contents = [contents] else: self.contents = contents self.attributes = attributes def to_string(self): yield '<{}'.format(self.tag) for (a, v) in self.attributes.items(): yield ' {}="{}"'.format(a, v) if self.contents is None: yield '/>' else : yield '>' for c in self.contents: if isinstance(c, TAG): for i in c.to_string(): yield i else: yield c yield '</{}>'.format(self.tag) def to_string_b(self, builder=None): global isinstance, basestring def isbasestring(c, isinstance=isinstance, basestring=basestring): # some inlining return isinstance(c, basestring) if builder is None: iamroot = True builder = ET.TreeBuilder() else: iamroot = False #don't close+flush the builder builder.start(self.tag, self.attributes) if self.contents is not None: for c in self.contents: if (isbasestring(c)): builder.data(c) else: for _ in c.to_string_b(builder): pass builder.end(self.tag) # this is a yield *ONLY* to preserve the interface # of to_string()! if you can change the calling # code easily, use return instead! if iamroot: yield ET.tostring(builder.close()) class H1(TAG): def __init__(self, contents=None, **attributes): TAG.__init__(self, 'H1', contents, **attributes) class H2(TAG): def __init__(self, contents=None, **attributes): TAG.__init__(self, 'H2', contents, **attributes) tree = H1(["This is some ", H2("test input", id="abcd", cls="efgh"), " and trailing text"]) print ''.join(tree.to_string()) print ''.join(tree.to_string_b()) </code></pre>

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