parser

This module contains the parsing logic for taking rule text in the specified grammar and converting it to an abstract syntax tree that can later be evaluated.

• utilities

Classes

class Parser(debug=False)

Bases: ParserBase

The parser class for the rule grammar. This class contains many ply specific members to define the various components of the grammar allowing it to be parsed and reduced into an abstract syntax tree (AST). Once the AST has been constructed it can then be evaluated multiple times. To make the evaluation more efficient, nodes within the AST that are able to be reduced are while the parsing is taking place. This reduction phase involves evaluation, causing EvaluationError exceptions to be raised during parsing.

__init__(debug=False)

Parameters:

debug (bool) – Whether or not to enable debugging features when using the ply API.

class ParserBase(debug=False)

Bases: object

A base class for parser objects to inherit from. This does not provide any grammar related definitions.

__init__(debug=False)

Parameters:

debug (bool) – Whether or not to enable debugging features when using the ply API.

parse(text, context, **kwargs)

Parse the specified text in an abstract syntax tree of nodes that can later be evaluated. This is done in two phases. First, the syntax is parsed and a tree of deferred / uninitialized AST nodes are constructed. Next each node is built recursively using it’s respective rule_engine.ast.ASTNodeBase.build().

Parameters:

• text (str) – The grammar text to parse into an AST.

• context (Context) – A context for specifying parsing and evaluation options.

Returns:

The parsed AST statement.

Return type:

Statement

precedence = ()

The precedence for operators.

reserved_words = {}

A mapping of literal words which are reserved to their corresponding grammar names.