>>> u'aあä'.encode('ascii', 'ignore')
'a'

Decode the string you get back, using either the charset in the the appropriate meta tag in the response or in the Content-Type header, then encode.

The method encode(encoding, errors) accepts custom handlers for errors. The default values, besides ignore, are:

>>> u'aあä'.encode('ascii', 'replace')
b'a??'
>>> u'aあä'.encode('ascii', 'xmlcharrefreplace')
b'aあä'
>>> u'aあä'.encode('ascii', 'backslashreplace')
b'a\\u3042\\xe4'

See https://docs.python.org/3/library/stdtypes.html#str.encode

Use the Unidecode package to transliterate the string.

>>> import unidecode
>>> unidecode.unidecode(u'Gavin O’Connor')
"Gavin O'Connor"

See unicodedata.normalize

title = u"Klüft skräms inför på fédéral électoral große"
import unicodedata
unicodedata.normalize('NFKD', title).encode('ascii', 'ignore')
'Kluft skrams infor pa federal electoral groe'

That's not a corresponding ASCII string, it's a UTF-8 string. ASCII, definitionally, cannot represent the whole of the Unicode range; UTF-8 can.

To perform the conversion, use the .encode method of unicode objects:

u'S\xe9parateur'.encode('utf-8')

produces 'S\xc3\xa9parateur'.

The Unicode characters u'\xce0' and u'\xc9' do not have any corresponding ASCII values. So, if you don't want to lose data, you have to encode that data in some way that's valid as ASCII. Options include:

>>> print s.encode('ascii', errors='backslashreplace')
ABRA\xc3O JOS\xc9
>>> print s.encode('ascii', errors='xmlcharrefreplace')
ABRAÃO JOSÉ
>>> print s.encode('unicode-escape')
ABRA\xc3O JOS\xc9
>>> print s.encode('punycode')
ABRAO JOS-jta5e

All of these are ASCII strings, and contain all of the information from your original Unicode string (so they can all be reversed without loss of data), but none of them are all that pretty for an end-user (and none of them can be reversed just by decode('ascii')).

See str.encode, Python Specific Encodings, and Unicode HOWTO for more info.

As a side note, when some people say "ASCII", they really don't mean "ASCII" but rather "any 8-bit character set that's a superset of ASCII" or "some particular 8-bit character set that I have in mind". If that's what you meant, the solution is to encode to the right 8-bit character set:

>>> s.encode('utf-8')
'ABRA\xc3\x83O JOS\xc3\x89'
>>> s.encode('cp1252')
'ABRA\xc3O JOS\xc9'
>>> s.encode('iso-8859-15')
'ABRA\xc3O JOS\xc9'

The hard part is knowing which character set you meant. If you're writing both the code that produces the 8-bit strings and the code that consumes it, and you don't know any better, you meant UTF-8. If the code that consumes the 8-bit strings is, say, the open function or a web browser that you're serving a page to or something else, things are more complicated, and there's no easy answer without a lot more information.

So I literally found the answer 2 minutes after posting this.

The answer is to do the following in Python 2.7

rawdata = '\u003c!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"\u003e'
asciistr = rawdata.decode("raw_unicode_escape")
print asciistr

You can convert the file easily enough just using the unicode function, but you'll run into problems with Unicode characters without a straight ASCII equivalent.

This blog recommends the unicodedata module, which seems to take care of roughly converting characters without direct corresponding ASCII values, e.g.

>>> title = u"Klüft skräms inför på fédéral électoral große"

is typically converted to

Klft skrms infr p fdral lectoral groe

which is pretty wrong. However, using the unicodedata module, the result can be much closer to the original text:

>>> import unicodedata
>>> unicodedata.normalize('NFKD', title).encode('ascii','ignore')
'Kluft skrams infor pa federal electoral groe'