1
2
3
4
5 """MIME-Type Parser
6
7 This module provides basic functions for handling mime-types. It can handle
8 matching mime-types against a list of media-ranges. See section 14.1 of the
9 HTTP specification [RFC 2616] for a complete explanation.
10
11 http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.1
12
13 Contents:
14 - parse_mime_type(): Parses a mime-type into its component parts.
15 - parse_media_range(): Media-ranges are mime-types with wild-cards and a 'q'
16 quality parameter.
17 - quality(): Determines the quality ('q') of a mime-type when
18 compared against a list of media-ranges.
19 - quality_parsed(): Just like quality() except the second parameter must be
20 pre-parsed.
21 - best_match(): Choose the mime-type with the highest quality ('q')
22 from a list of candidates.
23 """
24
25 __version__ = '0.1.3'
26 __author__ = 'Joe Gregorio'
27 __email__ = 'joe@bitworking.org'
28 __license__ = 'MIT License'
29 __credits__ = ''
30
31
33 """Parses a mime-type into its component parts.
34
35 Carves up a mime-type and returns a tuple of the (type, subtype, params)
36 where 'params' is a dictionary of all the parameters for the media range.
37 For example, the media range 'application/xhtml;q=0.5' would get parsed
38 into:
39
40 ('application', 'xhtml', {'q', '0.5'})
41 """
42 parts = mime_type.split(';')
43 params = dict([tuple([s.strip() for s in param.split('=', 1)])\
44 for param in parts[1:]
45 ])
46 full_type = parts[0].strip()
47
48
49 if full_type == '*':
50 full_type = '*/*'
51 (type, subtype) = full_type.split('/')
52
53 return (type.strip(), subtype.strip(), params)
54
55
77
78
80 """Find the best match for a mime-type amongst parsed media-ranges.
81
82 Find the best match for a given mime-type against a list of media_ranges
83 that have already been parsed by parse_media_range(). Returns a tuple of
84 the fitness value and the value of the 'q' quality parameter of the best
85 match, or (-1, 0) if no match was found. Just as for quality_parsed(),
86 'parsed_ranges' must be a list of parsed media ranges.
87 """
88 best_fitness = -1
89 best_fit_q = 0
90 (target_type, target_subtype, target_params) =\
91 parse_media_range(mime_type)
92 for (type, subtype, params) in parsed_ranges:
93 type_match = (type == target_type or\
94 type == '*' or\
95 target_type == '*')
96 subtype_match = (subtype == target_subtype or\
97 subtype == '*' or\
98 target_subtype == '*')
99 if type_match and subtype_match:
100 param_matches = reduce(lambda x, y: x + y, [1 for (key, value) in \
101 target_params.iteritems() if key != 'q' and \
102 params.has_key(key) and value == params[key]], 0)
103 fitness = (type == target_type) and 100 or 0
104 fitness += (subtype == target_subtype) and 10 or 0
105 fitness += param_matches
106 if fitness > best_fitness:
107 best_fitness = fitness
108 best_fit_q = params['q']
109
110 return best_fitness, float(best_fit_q)
111
112
114 """Find the best match for a mime-type amongst parsed media-ranges.
115
116 Find the best match for a given mime-type against a list of media_ranges
117 that have already been parsed by parse_media_range(). Returns the 'q'
118 quality parameter of the best match, 0 if no match was found. This function
119 bahaves the same as quality() except that 'parsed_ranges' must be a list of
120 parsed media ranges.
121 """
122
123 return fitness_and_quality_parsed(mime_type, parsed_ranges)[1]
124
125
127 """Return the quality ('q') of a mime-type against a list of media-ranges.
128
129 Returns the quality 'q' of a mime-type when compared against the
130 media-ranges in ranges. For example:
131
132 >>> quality('text/html','text/*;q=0.3, text/html;q=0.7,
133 text/html;level=1, text/html;level=2;q=0.4, */*;q=0.5')
134 0.7
135
136 """
137 parsed_ranges = [parse_media_range(r) for r in ranges.split(',')]
138
139 return quality_parsed(mime_type, parsed_ranges)
140
141
143 """Return mime-type with the highest quality ('q') from list of candidates.
144
145 Takes a list of supported mime-types and finds the best match for all the
146 media-ranges listed in header. The value of header must be a string that
147 conforms to the format of the HTTP Accept: header. The value of 'supported'
148 is a list of mime-types. The list of supported mime-types should be sorted
149 in order of increasing desirability, in case of a situation where there is
150 a tie.
151
152 >>> best_match(['application/xbel+xml', 'text/xml'],
153 'text/*;q=0.5,*/*; q=0.1')
154 'text/xml'
155 """
156 split_header = _filter_blank(header.split(','))
157 parsed_header = [parse_media_range(r) for r in split_header]
158 weighted_matches = []
159 pos = 0
160 for mime_type in supported:
161 weighted_matches.append((fitness_and_quality_parsed(mime_type,
162 parsed_header), pos, mime_type))
163 pos += 1
164 weighted_matches.sort()
165
166 return weighted_matches[-1][0][1] and weighted_matches[-1][2] or ''
167
168
170 for s in i:
171 if s.strip():
172 yield s
173