Parse the Accept-Language header as defined in RFC2616.

Author: Alexander Smishlajev

roundup/cgi/accept_language.py

@@ -0,0 +1,75 @@
+"""Parse the Accept-Language header as defined in RFC2616.
+
+See http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.4
+for details.  This module should follow the spec.
+Author: Hernan M. Foffani ([email protected])
+Some use samples:
+
+>>> parse("da, en-gb;q=0.8, en;q=0.7")
+['da', 'en_gb', 'en']
+>>> parse("en;q=0.2, fr;q=1")
+['fr', 'en']
+>>> parse("zn; q = 0.2 ,pt-br;q =1")
+['pt_br', 'zn']
+>>> parse("es-AR")
+['es_AR']
+>>> parse("es-es-cat")
+['es_es_cat']
+>>> parse("")
+[]
+>>> parse(None)
+[]
+>>> parse("   ")
+[]
+>>> parse("en,")
+['en']
+"""
+
+import re
+import heapq
+
+# regexp for languange-range search
+nqlre = "([A-Za-z]+[-[A-Za-z]+]*)$"
+# regexp for languange-range search with quality value
+qlre  = "([A-Za-z]+[-[A-Za-z]+]*);q=([\d\.]+)"
+# both
+lre   = re.compile(nqlre + "|" + qlre)
+
+ascii = ''.join([chr(x) for x in xrange(256)])
+whitespace = ' \t\n\r\v\f'
+
+def parse(language_header):
+    """parse(string_with_accept_header_content) -> languages list"""
+
+    if language_header is None: return []
+
+    # strip whitespaces.
+    lh = language_header.translate(ascii, whitespace)
+
+    # if nothing, return
+    if lh == "": return []
+
+    # split by commas and parse the quality values.
+    pls = [lre.findall(x) for x in lh.split(',')]
+
+    # drop uncomformant
+    qls = [x[0] for x in pls if len(x) > 0]
+
+    # use a heap queue to sort by quality values.
+    # the value of each item is 1.0 complement.
+    pq = []
+    for l in qls:
+        if l[0] != '':
+            heapq.heappush(pq, (0.0, l[0]))
+        else:
+            heapq.heappush(pq, (1.0-float(l[2]), l[1]))
+
+    # get the languages ordered by quality
+    # and replace - by _
+    return [x[1].replace('-','_') for x in pq]
+
+if __name__ == "__main__":
+    import doctest
+    doctest.testmod()
+
+# vim: set et sts=4 sw=4 :