ANN: pyparsing1.4.7

Paul McGuire ptmcg at
Sun Jul 22 17:06:39 CEST 2007

I just uploaded the latest release (v1.4.7) of pyparsing, and I'm
happy to say, it is not a very big release - this module is getting
to be quite stable.  A few bug-fixes, and one significant notation
enhancement: setResultsNames gains a big shortcut in this release
(see below).  No new examples in this release, sorry.

Here are the notes:

- NEW NOTATION SHORTCUT: ParserElement now accepts results names
  using a notational shortcut, following the expression with the
  results name in parentheses.  So this:

    stats = "AVE:" + realNum.setResultsName("average") + \
            "MIN:" + realNum.setResultsName("min") + \
            "MAX:" + realNum.setResultsName("max")

  can now be written as this:

    stats = "AVE:" + realNum("average") + \
            "MIN:" + realNum("min") + \
            "MAX:" + realNum("max")

  The intent behind this change is to make it simpler to define
  results names for significant fields within the expression, while
  keeping the grammar syntax clean and uncluttered.

- Fixed bug when packrat parsing is enabled, with cached ParseResults
  being updated by subsequent parsing.  Reported on the pyparsing
  wiki by Kambiz, thanks!

- Fixed bug in operatorPrecedence for unary operators with left
  associativity, if multiple operators were given for the same term.

- Fixed bug in example, corrected precedence of "and"
  vs. "or" operations.

- Fixed bug in Dict class, in which keys were converted to strings
  whether they needed to be or not.  Have narrowed this logic to
  convert keys to strings only if the keys are ints (which would
  confuse __getitem__ behavior for list indexing vs. key lookup).

- Added ParserElement method setBreak(), which will invoke the pdb
  module's set_trace() function when this expression is about to be

- Fixed bug in StringEnd in which reading off the end of the input
  string raises an exception - should match.  Resolved while
  answering a question for Shawn on the pyparsing wiki.

Download pyparsing 1.4.7 at
The pyparsing Wiki is at

-- Paul

Pyparsing is a pure-Python class library for quickly developing
recursive-descent parsers.  Parser grammars are assembled directly in
the calling Python code, using classes such as Literal, Word,
OneOrMore, Optional, etc., combined with operators '+', '|', and '^'
for And, MatchFirst, and Or.  No separate code-generation or external
files are required.  Pyparsing can be used in many cases in place of
regular expressions, with shorter learning curve and greater
readability and maintainability.  Pyparsing comes with a number of
parsing examples, including:
- "Hello, World!" (English, Korean, Greek, and Spanish(new))
- chemical formulas
- configuration file parser
- web page URL extractor
- 5-function arithmetic expression parser
- subset of CORBA IDL
- chess portable game notation
- simple SQL parser
- Mozilla calendar file parser
- EBNF parser/compiler
- Python value string parser (lists, dicts, tuples, with nesting)
  (safe alternative to eval)
- HTML tag stripper
- S-expression parser
- macro substitution preprocessor

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