id,summary,reporter,owner,description,type,status,priority,component,severity,resolution,keywords,cc
173,Python regular expression named groups breaks (?) pyyaml,anonymous,xi,"I'm using pyyaml 3.09 in Python 2.6.5 on Ubuntu 10.04 LTS. 

I have a yaml file I used for configuration of a web server (tornado), and the section of my file causing issues looks like this: 

{{{
RequestHandlers:
  # [ path, handler class, [whitelist] ]
   - [/stats, myapp.core.Stats, [127.0.0.1, 10.0.0.0/8]]
   - [r'/(?P<id>.*)', myapp.core.Foo, [127.0.0.1, 192.168.0.0/16]]
   - [/.*, myapp.core.MainHandler, []]
}}}


When this gets loaded, pyyaml yells at me. Here's a python interpreter session: 

============================================
{{{
Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56) 
[GCC 4.4.3] on linux2
Type ""help"", ""copyright"", ""credits"" or ""license"" for more information.
>>> import yaml
>>> stream = open('etc/subzero.yaml')
>>> config = yaml.load(stream)
Traceback (most recent call last):
  File ""<stdin>"", line 1, in <module>
  File ""build/bdist.linux-i686/egg/yaml/__init__.py"", line 58, in load
    
  File ""build/bdist.linux-i686/egg/yaml/constructor.py"", line 42, in get_single_data
  File ""build/bdist.linux-i686/egg/yaml/composer.py"", line 36, in get_single_node
  File ""build/bdist.linux-i686/egg/yaml/composer.py"", line 55, in compose_document
  File ""build/bdist.linux-i686/egg/yaml/composer.py"", line 84, in compose_node
  File ""build/bdist.linux-i686/egg/yaml/composer.py"", line 133, in compose_mapping_node
  File ""build/bdist.linux-i686/egg/yaml/composer.py"", line 82, in compose_node
  File ""build/bdist.linux-i686/egg/yaml/composer.py"", line 111, in compose_sequence_node
  File ""build/bdist.linux-i686/egg/yaml/composer.py"", line 82, in compose_node
  File ""build/bdist.linux-i686/egg/yaml/composer.py"", line 110, in compose_sequence_node
  File ""build/bdist.linux-i686/egg/yaml/parser.py"", line 93, in check_event
  File ""build/bdist.linux-i686/egg/yaml/parser.py"", line 479, in parse_flow_sequence_entry
yaml.parser.ParserError: while parsing a flow sequence
  in ""etc/myapp.yaml"", line 35, column 5
expected ',' or ']', but got '?'
  in ""etc/myapp.yaml"", line 35, column 10
}}}
============================================

Line 35 is:
{{{
   - [r'/(?P<id>.*)', myapp.core.Foo, [127.0.0.1, 192.168.0.0/16]]
}}}
I'm wondering why it's choking here. Disabling this line causes everything to work perfectly well. The question mark is a special case in YAML, but (I thought) only when it's accompanied by a space. I don't recall ever needing to escape anything inside of a yaml file, but I tried escaping the '?'. Not sure what to try next. If I double-quote like ""r'/(?P<id>.*)'"" then it'll be a double-quoted string on the other end of the load as well, which doesn't help me. 

Clue hereby solicited. ",defect,closed,normal,pyyaml,normal,invalid,,