How to fetch a non-ascii url with Python urlopen?

Question

I need to fetch data from a URL with non-ascii characters but urllib2.urlopen refuses to open the resource and raises:

UnicodeEncodeError: 'ascii' codec can't encode character u'\u0131' in position 26: ordinal not in range(128)

I know the URL is not standards compliant but I have no chance to change it.

What is the way to access a resource pointed by a URL containing non-ascii characters using Python?

edit: In other words, can / how urlopen open a URL like:

http://example.org/Ñöñ-ÅŞÇİİ/

Answer 1

Strictly speaking URIs can't contain non-ASCII characters; what you have there is an IRI.

To convert an IRI to a plain ASCII URI:

• non-ASCII characters in the hostname part of the address have to be encoded using the Punycode-based IDNA algorithm;

• non-ASCII characters in the path, and most of the other parts of the address have to be encoded using UTF-8 and %-encoding, as per Ignacio's answer.

So:

import re, urlparse

def urlEncodeNonAscii(b):
    return re.sub('[\x80-\xFF]', lambda c: '%%%02x' % ord(c.group(0)), b)

def iriToUri(iri):
    parts= urlparse.urlparse(iri)
    return urlparse.urlunparse(
        part.encode('idna') if parti==1 else urlEncodeNonAscii(part.encode('utf-8'))
        for parti, part in enumerate(parts)
    )

>>> iriToUri(u'http://www.a\u0131b.com/a\u0131b')
'http://www.xn--ab-hpa.com/a%c4%b1b'

(Technically this still isn't quite good enough in the general case because urlparse doesn't split away any user:pass@ prefix or :port suffix on the hostname. Only the hostname part should be IDNA encoded. It's easier to encode using normal urllib.quote and .encode('idna') at the time you're constructing a URL than to have to pull an IRI apart.)