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