def _xml_escape(data):
    """Escape &, <, >, ", ', etc. in a string of data."""

    # ampersand must be replaced first
    from_symbols = '&><"\''
    to_symbols = ('&'+s+';' for s in "amp gt lt quot apos".split())
    for from_,to_ in zip(from_symbols, to_symbols):
        data = data.replace(from_, to_)
    return data
Escape &, <, >, ", ', etc. in a string of data.
src/pkg_resources/_vendor/pyparsing.py