openstack.py 文件源码

def grammar():
    """Define the query grammar.

    Backus-Naur form (BNF) of the grammar::

        <grammar> ::= "*" | <items>
          <items> ::= <item> | <item> <whitespace> <items>
           <item> ::= <key>:<value>

    Given that the pyparsing library defines the grammar in a BNF-like style, for the details of the tokens not
    specified above check directly the source code.

    Returns:
        pyparsing.ParserElement: the grammar parser.

    """
    quoted_string = pp.quotedString.copy().addParseAction(pp.removeQuotes)  # Both single and double quotes are allowed

    # Key-value tokens: key:value
    # Lowercase key, all printable characters except the parentheses that are part of the global grammar for the value
    key = pp.Word(pp.srange('[a-z0-9-_.]"'), min=2)('key')
    all_but_par = ''.join([c for c in pp.printables if c not in ('(', ')', '{', '}')])
    value = (quoted_string | pp.Word(all_but_par))('value')
    item = pp.Combine(key + ':' + value)

    # Final grammar, see the docstring for its BNF based on the tokens defined above
    # Groups are used to split the parsed results for an easy access
    return pp.Group(pp.Literal('*')('all')) | pp.OneOrMore(pp.Group(item))