Pyparsing 3.1.0

[ptmcg]

NOTE: In the future release 3.2.0, use of many of the pre-PEP8 methods (such as ParserElement.parseString) will start to raise DeprecationWarnings. 3.2.0 should get released some time later in 2023. I currently plan to completely drop the pre-PEP8 methods in pyparsing 4.0, though we won't see that release until at least late 2023 if not 2024. So there is plenty of time to convert existing parsers to the new function names before the old functions are completely removed. (Big help from Devin J. Pohly in structuring the code to enable this peaceful transition.)

Version 3.2.0 will also discontinue support for Python versions 3.6 and 3.7.

Version 3.1.0 - June, 2023

API CHANGES

• A slight change has been implemented when unquoting a quoted string parsed using the QuotedString class. Formerly, when unquoting and processing whitespace markers such as \t and \n, these substitutions would occur first, and then any additional '' escaping would be done on the resulting string. This would parse "\n" as "<newline>". Now escapes and whitespace markers are all processed in a single pass working left to right, so the quoted string "\n" would get unquoted to "\n" (a backslash followed by "n"). Fixes issue QuotedString unquote_results doesn't understand escaped whitespace #474 raised by jakeanq, thanks!

• Reworked delimited_list function into the new DelimitedList class. DelimitedList has the same constructor interface as delimited_list, and in this release, delimited_list changes from a function to a synonym for DelimitedList. delimited_list and the older delimitedList method will be deprecated in a future release, in favor of DelimitedList.

• ParserElement.validate() is deprecated. It predates the support for left-recursive parsers, and was prone to false positives (warning that a grammar was invalid when it was in fact valid). It will be removed in a future pyparsing release. In its place, developers should use debugging and analytical tools, such as ParserElement.set_debug() and ParserElement.create_diagram(). (Raised in Issue Semantics of validate() is unclear #444, thanks Andrea Micheli!)

NEW FEATURES AND ENHANCEMENTS

• Optional(expr) may now be written as expr | ""

  This will make this code:

  "{" + Optional(Literal("A") | Literal("a")) + "}"
  

  writable as:

  "{" + (Literal("A") | Literal("a") | "") + "}"
  

  Some related changes implemented as part of this work:

  • Literal("") now internally generates an Empty() (and no longer raises an exception)
  • Empty is now a subclass of Literal

  Suggested by Antony Lee (issue Support ... | "" as alias for Opt(...) #412), PR (Use Literal.__new__ to select optimized subclasses #413) by Devin J. Pohly.

• Added new class method ParserElement.using_each, to simplify code that creates a sequence of Literals, Keywords, or other ParserElement subclasses.

  For instance, to define suppressible punctuation, you would previously write:

  LPAR, RPAR, LBRACE, RBRACE, SEMI = map(Suppress, "(){};")
  

  You can now write:

  LPAR, RPAR, LBRACE, RBRACE, SEMI = Suppress.using_each("(){};")
  

  using_each will also accept optional keyword args, which it will pass through to the class initializer. Here is an expression for single-letter variable names that might be used in an algebraic expression:

  algebra_var = MatchFirst(
      Char.using_each(string.ascii_lowercase, as_keyword=True)
  )
  

• Added new builtin python_quoted_string, which will match any form of single-line or multiline quoted strings defined in Python. (Inspired by discussion with Andreas Schörgenhumer in Issue pyparsing.python_style_comment.suppress() does not work with multi-line strings #421.)

• Extended expr[] notation for repetition of expr to accept a slice, where the slice's stop value indicates a stop_on expression:

  test = "BEGIN aaa bbb ccc END"
  BEGIN, END = Keyword.using_each("BEGIN END".split())
  body_word = Word(alphas)
  
  expr = BEGIN + Group(body_word[...:END]) + END
  # equivalent to
  # expr = BEGIN + Group(ZeroOrMore(body_word, stop_on=END)) + END
  
  print(expr.parse_string(test))
  

  Prints:

  ['BEGIN', ['aaa', 'bbb', 'ccc'], 'END']
  

• Added named field "url" to pyparsing.common.url, returning the entire parsed URL string.

• Added bool embed argument to ParserElement.create_diagram(). When passed as True, the resulting diagram will omit the <DOCTYPE>, <HEAD>, and <BODY> tags so that it can be embedded in other HTML source. (Useful when embedding a call to create_diagram() in a PyScript HTML page.)

• Added recurse argument to ParserElement.set_debug to set the debug flag on an expression and all of its sub-expressions. Requested by multimeric in Issue Recursively enable debug #399.

• Added '·' (Unicode MIDDLE DOT) to the set of Latin1.identbodychars.

• ParseResults now has a new method deepcopy(), in addition to the current copy() method. copy() only makes a shallow copy - any contained ParseResults are copied as references - changes in the copy will be seen as changes in the original. In many cases, a shallow copy is sufficient, but some applications require a deep copy. deepcopy() makes a deeper copy: any contained ParseResults or other mappings or containers are built with copies from the original, and do not get changed if the original is later changed. Addresses issue Unexpected behaviour of ParseResults.copy() with nested ParseResults #463, reported by Bryn Pickering.

• Added new class property identifier to all Unicode set classes in pyparsing.unicode, using the class's values for cls.identchars and cls.identbodychars. Now Unicode-aware parsers that formerly wrote:

  ppu = pyparsing.unicode
  ident = Word(ppu.Greek.identchars, ppu.Greek.identbodychars)
  

  can now write:

  ident = ppu.Greek.identifier
  # or
  # ident = ppu.????????.identifier
  

• Error messages from MatchFirst and Or expressions will try to give more details if one of the alternatives matches better than the others, but still fails. Question raised in Issue Confusing error message out of MatchFirst #464 by msdemlei, thanks!

BUG FIXES AND GENERAL CHANGES

• Added support for Python 3.12.

• Updated ci.yml permissions to limit default access to source - submitted by Joyce Brum of Google. Thanks so much!

• Updated create_diagram() code to be compatible with railroad-diagrams package version 3.0. Fixes Issue Badly rendered railroad diagram #477 (railroad diagrams generated with black bars), reported by Sam Morley-Short.

• Fixed bug in NotAny, where parse actions on the negated expr were not being run. This could cause NotAny to incorrectly fail if the expr would normally match, but would fail to match if a condition used as a parse action returned False. Fixes Issue NotAny(FollowedBy()) failing #482, raised by byaka, thank you!

• Fixed create_diagram() to accept keyword args, to be passed through to the template.render() method to generate the output HTML (PR submitted by Aussie Schnore, good catch!)

• Fixed bug in python_quoted_string regex.

• Fixed bug when parse actions returned an empty string for an expression that had a results name, that the results name was not saved. That is:

  expr = Literal("X").add_parse_action(lambda tokens: "")("value")
  result = expr.parse_string("X")
  print(result["value"])
  

  would raise a KeyError. Now empty strings will be saved with the associated results name. Raised in Issue "" as add_parse_action's result removes result name from ParseResults #470 by Nicco Kunzmann, thank you.

• Fixed bug in SkipTo where ignore expressions were not properly handled while scanning for the target expression. Issue SkipTo Erroneously Steps Into Grammar's ignoreExpr #475, reported by elkniwt, thanks (this bug has been there for a looooong time!).

• Fixed bug in Word when max=2. Also added performance enhancement when specifying exact argument. Reported in issue Word with max= parses incorrectly #409 by panda-34, nice catch!

• Word arguments are now validated if min and max are both given, that min <= max; raises ValueError if values are invalid.

• Fixed bug in srange, when parsing escaped '/' and '' inside a range set.

• Fixed exception messages for some ParserElements with custom names, which instead showed their contained expression names.

• Fixed bug in pyparsing.common.url, when input URL is not alone on an input line. Fixes Issue ZeroOrMore can only handle one URL #459, reported by David Kennedy.

• Multiple added and corrected type annotations. With much help from Stephen Rosen, thanks!

• Some documentation and error message clarifications on pyparsing's keyword logic, cited by Basil Peace.

• General docstring cleanup for Sphinx doc generation, PRs submitted by Devin J. Pohly. A dirty job, but someone has to do it - much appreciated!

EXAMPLE UPDATES

• Added tag_emitter.py to examples. This example demonstrates how to insert tags into your parsed results that are not part of the original parsed text.

• Added bf.py Brainf*ck parser/executor example. Illustrates using a pyparsing grammar to parse language syntax, and attach executable AST nodes to the parsed results.

• invRegex.py example renamed to inv_regex.py and updated to PEP-8 variable and method naming. PR submitted by Ross J. Duff, thanks!

• Removed examples sparser.py and pymicko.py, since each included its own GPL license in the header. Since this conflicts with pyparsing's MIT license, they were removed from the distribution to avoid confusion among those making use of them in their own projects.

• Updated the lucene_grammar.py example (better support for '*' and '?' wildcards) and corrected the test cases - brought to my attention by Elijah Nicol, good catch!

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This discussion was created from the release Pyparsing 3.1.0.