Module util

Load a grammar from a file, and build a parser based on that grammar. The parser depends on the grammar format, and might also depend on properties of the grammar itself.

The following grammar formats are currently supported:

• 'cfg' (CFGs: ContextFreeGrammar)
• 'pcfg' (probabilistic CFGs: WeightedGrammar)
• 'fcfg' (feature-based CFGs: ContextFreeGrammar)

Parameters:

• grammar_url (str) - A URL specifying where the grammar is located. The default protocol is "nltk:", which searches for the file in the the NLTK data package.
• trace (int) - The level of tracing that should be used when parsing a text. 0 will generate no tracing output; and higher numbers will produce more verbose tracing output.
• parser - The class used for parsing; should be ChartParser or a subclass. If None, the class depends on the grammar format.
• chart_class - The class used for storing the chart; should be Chart or a subclass. Only used for CFGs and feature CFGs. If None, the chart class depends on the grammar format.
• beam_size (int) - The maximum length for the parser's edge queue. Only used for probabilistic CFGs.
• load_args - Keyword parameters used when loading the grammar. See data.load for more information.

Parses a string with one test sentence per line. Lines can optionally begin with:

• a bool, saying if the sentence is grammatical or not, or
• an int, giving the number of parse trees is should have,

The result information is followed by a colon, and then the sentence. Empty lines and lines beginning with a comment char are ignored.

Parameters:

• comment_chars - str of possible comment characters.

Returns:

a list of tuple of sentences and expected results, where a sentence is a list of str, and a result is None, or bool, or int