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"""Parse (absolute and relative) URLs.
See RFC 1808: "Relative Uniform Resource Locators", by R. Fielding,
UC Irvine, June 1995.
"""
# Standard/builtin Python modules
import string
from string import joinfields, splitfields, rfind
# A classification of schemes ('' means apply by default)
uses_relative = ['ftp', 'http', 'gopher', 'nntp', 'wais', 'file',
'https', 'shttp',
'prospero', '']
uses_netloc = ['ftp', 'http', 'gopher', 'nntp', 'telnet', 'wais',
'file',
'https', 'shttp', 'snews',
'prospero', '']
non_hierarchical = ['gopher', 'hdl', 'mailto', 'news', 'telnet', 'wais',
'snews',
]
uses_params = ['ftp', 'hdl', 'prospero', 'http',
'https', 'shttp',
'']
uses_query = ['http', 'wais',
'https', 'shttp',
'gopher',
'']
uses_fragment = ['ftp', 'hdl', 'http', 'gopher', 'news', 'nntp', 'wais',
'https', 'shttp', 'snews',
'file', 'prospero', '']
# Characters valid in scheme names
scheme_chars = string.letters + string.digits + '+-.'
MAX_CACHE_SIZE = 20
_parse_cache = {}
def clear_cache():
"""Clear the parse cache."""
global _parse_cache
_parse_cache = {}
def urlparse(url, scheme = '', allow_fragments = 1):
"""Parse a URL into 6 components:
<scheme>://<netloc>/<path>;<params>?<query>#<fragment>
Return a 6-tuple: (scheme, netloc, path, params, query, fragment).
Note that we don't break the components up in smaller bits
(e.g. netloc is a single string) and we don't expand % escapes."""
key = url, scheme, allow_fragments
cached = _parse_cache.get(key, None)
if cached:
return cached
if len(_parse_cache) >= MAX_CACHE_SIZE: # avoid runaway growth
clear_cache()
find = string.find
netloc = path = params = query = fragment = ''
i = find(url, ':')
if i > 0:
if url[:i] == 'http': # optimize the common case
scheme = string.lower(url[:i])
url = url[i+1:]
if url[:2] == '//':
i = find(url, '/', 2)
if i < 0:
i = len(url)
netloc = url[2:i]
url = url[i:]
if allow_fragments:
i = string.rfind(url, '#')
if i >= 0:
fragment = url[i+1:]
url = url[:i]
i = find(url, '?')
if i >= 0:
query = url[i+1:]
url = url[:i]
i = find(url, ';')
if i >= 0:
params = url[i+1:]
url = url[:i]
tuple = scheme, netloc, url, params, query, fragment
_parse_cache[key] = tuple
return tuple
for c in url[:i]:
if c not in scheme_chars:
break
else:
scheme, url = string.lower(url[:i]), url[i+1:]
if scheme in uses_netloc:
if url[:2] == '//':
i = find(url, '/', 2)
if i < 0:
i = len(url)
netloc, url = url[2:i], url[i:]
if allow_fragments and scheme in uses_fragment:
i = string.rfind(url, '#')
if i >= 0:
url, fragment = url[:i], url[i+1:]
if scheme in uses_query:
i = find(url, '?')
if i >= 0:
url, query = url[:i], url[i+1:]
if scheme in uses_params:
i = find(url, ';')
if i >= 0:
url, params = url[:i], url[i+1:]
tuple = scheme, netloc, url, params, query, fragment
_parse_cache[key] = tuple
return tuple
def urlunparse((scheme, netloc, url, params, query, fragment)):
"""Put a parsed URL back together again. This may result in a
slightly different, but equivalent URL, if the URL that was parsed
originally had redundant delimiters, e.g. a ? with an empty query
(the draft states that these are equivalent)."""
if netloc or (scheme in uses_netloc and url[:2] == '//'):
if url[:1] != '/': url = '/' + url
url = '//' + (netloc or '') + url
if scheme:
url = scheme + ':' + url
if params:
url = url + ';' + params
if query:
url = url + '?' + query
if fragment:
url = url + '#' + fragment
return url
def urljoin(base, url, allow_fragments = 1):
"""Join a base URL and a possibly relative URL to form an absolute
interpretation of the latter."""
if not base:
return url
bscheme, bnetloc, bpath, bparams, bquery, bfragment = \
urlparse(base, '', allow_fragments)
scheme, netloc, path, params, query, fragment = \
urlparse(url, bscheme, allow_fragments)
if scheme != bscheme or scheme not in uses_relative:
return urlunparse((scheme, netloc, path,
params, query, fragment))
if scheme in uses_netloc:
if netloc:
return urlunparse((scheme, netloc, path,
params, query, fragment))
netloc = bnetloc
if path[:1] == '/':
return urlunparse((scheme, netloc, path,
params, query, fragment))
if not path:
return urlunparse((scheme, netloc, bpath,
params, query or bquery, fragment))
i = rfind(bpath, '/')
if i >= 0:
path = bpath[:i] + '/' + path
segments = splitfields(path, '/')
if segments[-1] == '.':
segments[-1] = ''
while '.' in segments:
segments.remove('.')
while 1:
i = 1
n = len(segments) - 1
while i < n:
if segments[i] == '..' and segments[i-1]:
del segments[i-1:i+1]
break
i = i+1
else:
break
if len(segments) == 2 and segments[1] == '..' and segments[0] == '':
segments[-1] = ''
elif len(segments) >= 2 and segments[-1] == '..':
segments[-2:] = ['']
return urlunparse((scheme, netloc, joinfields(segments, '/'),
params, query, fragment))
def urldefrag(url):
"""Removes any existing fragment from URL.
Returns a tuple of the defragmented URL and the fragment. If
the URL contained no fragments, the second element is the
empty string.
"""
s, n, p, a, q, frag = urlparse(url)
defrag = urlunparse((s, n, p, a, q, ''))
return defrag, frag
test_input = """
http://a/b/c/d
g:h = <URL:g:h>
http:g = <URL:http://a/b/c/g>
http: = <URL:http://a/b/c/d>
g = <URL:http://a/b/c/g>
./g = <URL:http://a/b/c/g>
g/ = <URL:http://a/b/c/g/>
/g = <URL:http://a/g>
//g = <URL:http://g>
?y = <URL:http://a/b/c/d?y>
g?y = <URL:http://a/b/c/g?y>
g?y/./x = <URL:http://a/b/c/g?y/./x>
. = <URL:http://a/b/c/>
./ = <URL:http://a/b/c/>
.. = <URL:http://a/b/>
../ = <URL:http://a/b/>
../g = <URL:http://a/b/g>
../.. = <URL:http://a/>
../../g = <URL:http://a/g>
../../../g = <URL:http://a/../g>
./../g = <URL:http://a/b/g>
./g/. = <URL:http://a/b/c/g/>
/./g = <URL:http://a/./g>
g/./h = <URL:http://a/b/c/g/h>
g/../h = <URL:http://a/b/c/h>
http:g = <URL:http://a/b/c/g>
http: = <URL:http://a/b/c/d>
http:?y = <URL:http://a/b/c/d?y>
http:g?y = <URL:http://a/b/c/g?y>
http:g?y/./x = <URL:http://a/b/c/g?y/./x>
"""
# XXX The result for //g is actually http://g/; is this a problem?
def test():
import sys
base = ''
if sys.argv[1:]:
fn = sys.argv[1]
if fn == '-':
fp = sys.stdin
else:
fp = open(fn)
else:
import StringIO
fp = StringIO.StringIO(test_input)
while 1:
line = fp.readline()
if not line: break
words = string.split(line)
if not words:
continue
url = words[0]
parts = urlparse(url)
print '%-10s : %s' % (url, parts)
abs = urljoin(base, url)
if not base:
base = abs
wrapped = '<URL:%s>' % abs
print '%-10s = %s' % (url, wrapped)
if len(words) == 3 and words[1] == '=':
if wrapped != words[2]:
print 'EXPECTED', words[2], '!!!!!!!!!!'
if __name__ == '__main__':
test()
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