import re
TAG = r"""
        <\s*
        (?!\s*[!"])
        (?P<close>\s*\/)?
        (?P<name>\w+)
        (
                [^'"\t >]+
            |
                "[^\"]*"['\"]*
            |
                '[^']*'['\"]*
            | 
                \s+
        )*
        (?P<selfcont>\s*\/\s*)?
        \s*>
      """
UNI = set(["br", "hr", "img", "input", "area", "link"])
INDENT = " "*4
def pretty_xmlish(s):
    """
        This is a robust, general indenter for XML-ish data. 
        Returns a list of lines.
    """
    data, offset, indent, prev = [], 0, 0, None
    for i in re.finditer(TAG, s, re.VERBOSE|re.MULTILINE):
        start, end = i.span()
        name = i.group("name")
        if start > offset:
            txt = []
            for x in textwrap.dedent(s[offset:start]).split("\n"):
                if x.strip():
                    txt.append(indent*INDENT + x)
            data.extend(txt)
        if i.group("close") and not (name in UNI and name==prev):
            indent = max(indent - 1, 0)
        data.append(indent*INDENT + i.group().strip())
        offset = end
        if not any([i.group("close"), i.group("selfcont"), name in UNI]):
            indent += 1
        prev = name
    return data

import re
TAG = r"""
        <\s*
        (?!\s*[!"])
        (?P<close>\s*\/)?
        (?P<name>\w+)
        (
                [^'"\t >]+
            |
                "[^\"]*"['\"]*
            |
                '[^']*'['\"]*
            | 
                \s+
        )*
        (?P<selfcont>\s*\/\s*)?
        \s*>
      """
UNI = set(["br", "hr", "img", "input", "area", "link"])
INDENT = " "*4
def pretty_xmlish(s):
    """
        This is a robust, general pretty-printer for XML-ish data. 
        Returns a list of lines.
    """
    data, offset, indent, prev = [], 0, 0, None
    for i in re.finditer(TAG, s, re.VERBOSE|re.MULTILINE):
        start, end = i.span()
        name = i.group("name")
        if start > offset:
            txt = []
            for x in textwrap.dedent(s[offset:start]).split("\n"):
                if x.strip():
                    txt.append(indent*INDENT + x)
            data.extend(txt)
        if i.group("close") and not (name in UNI and name==prev):
            indent = max(indent - 1, 0)
        data.append(indent*INDENT + i.group().strip())
        offset = end
        if not any([i.group("close"), i.group("selfcont"), name in UNI]):
            indent += 1
        prev = name
    return data

Robust pretty-printing for XML-like data

Python