fix: update pyparsing method names to resolve deprecation warnings

[RobertSundling]

Summary

Updates pyparsing method calls in formulas.py to use PEP8-compliant names, resolving deprecation warnings introduced in pyparsing 3.3.0 in December 2025. The PEP8-compliant names were introduced in pyparsing 3.0.0 in August 2021.

Problem

Starting with pyparsing 3.3.0, the library emits PyparsingDeprecationWarning for methods using the old camelCase naming convention:

PyparsingDeprecationWarning: 'setParseAction' deprecated - use 'set_parse_action'
PyparsingDeprecationWarning: 'setName' deprecated - use 'set_name'
PyparsingDeprecationWarning: 'parseString' deprecated - use 'parse_string'

These warnings appear when using periodictable for formula parsing, creating noise in applications and test suites.

Changes

Updated all pyparsing method calls in periodictable/formulas.py to use the new PEP8-compliant method names:

Old Method	New Method
setParseAction()	set_parse_action()
setName()	set_name()
parseString()	parse_string()

This was done using the pyparsing-provided migration tool: pyparsing.tools.cvt_pyparsing_pep8_names

Testing

• All existing tests pass (aside an from existing warning about the invalid escape code of \d inside a comment on line 529 of periodictable/xsf.py)
• Confirmed deprecation warnings are eliminated

References

• pyparsing 3.3.0 release notes

[bmaranville]

This seems like a very straightforward change... will you want a patch release on pypi after this, or are you working from source?

[RobertSundling]

will you want a patch release on pypi after this, or are you working from source?

For my projects that use periodictable, it's via pip and pypi. So it would be preferable if there could be a patch release there, too. (I do know that makes things a lot more complicated for you.)

[RobertSundling]

I also added >= 3.0.0 to the pyparsing line in pyproject.toml since this change will now also require at least version 3.0.0 of pyparsing.

[bmaranville]

I defer to @pkienzle on publishing new versions of periodictable, but I suspect we can do it next week. We have a publishing GH action set up, so we just have to update the release notes and push a new tag, after this is merged.

[pkienzle]

Some of these were addressed in #109. Need to compare against fix-104-type-hinting to see if I missed any.