Ask a Question

If you have questions about using Formulate, this page provides guidance on where and how to ask for help.

Where to Ask Questions

Depending on the nature of your question, there are several channels available:

GitHub Discussions

For general questions about using Formulate, feature requests, or to share your experience:

  • Visit the Formulate GitHub Discussions

  • Create a new discussion in the appropriate category (Q&A, Ideas, Show and Tell, etc.)

  • Be sure to check existing discussions first to see if your question has already been answered

GitHub Issues

For bug reports or specific technical issues:

  • Check the existing issues to see if your problem has already been reported

  • If not, create a new issue with details about your problem

  • Include information about your environment, steps to reproduce, and any error messages

Elsewhere in Scikit-HEP

If your question is really about the tool at the other end of the conversion — how TTreeFormula evaluates something, or what numexpr does with a particular dtype — that project’s own issue tracker will get you a better answer. The Scikit-HEP website lists the packages in the ecosystem and where each is discussed.

How to Ask Effective Questions

To get the best help possible, consider these tips when asking questions:

  1. Be Specific

    Clearly state what you’re trying to accomplish and where you’re stuck. Instead of “Formulate isn’t working,” try “I’m trying to convert this ROOT expression to numexpr and getting this specific error.”

  2. Include Context

    Provide relevant information about your environment:

    • Formulate version

    • Python version

    • Operating system

    • Any other relevant packages and their versions

  3. Show Minimal Examples

    Include the smallest possible code example that demonstrates your issue — the expression that fails, and what you expected instead:

    import formulate

# This converts fine
print(formulate.from_root("x + y").to_numexpr())

# This does not, and here is what it says
try:
    formulate.from_root("arr[0]").to_numexpr()
except ValueError as error:
    print(error)

    (x + y)
Matrix operations are forbidden in NumExpr.

    Reducing a long expression to the part that misbehaves is usually the step that answers the question by itself.

  4. Include Full Error Messages

    If you’re encountering an error, include the complete error message with traceback. Formulate’s parse errors carry a location and often a suggestion, and both are useful:

    try:
    formulate.from_root("a & b")
except formulate.ParseError as error:
    print(error)

    There was an error parsing the expression at or near this location
a & b
  ^

Here are some suggestions for how to fix the error:
- Use '&&' instead of '&'.

Here is the Lark error message:
No terminal matches '&' in the current parser context, at line 1 col 3

a & b
  ^
Expected one of: 
	* MINUS
	* COLON
	* PERCENT
	* "||"
	* LPAR
	* "!="
	* SLASH
	* LESSTHAN
	* RPAR
	* "&&"
	* "::"
	* COMMA
	* PLUS
	* ">="
	* "**"
	* MORETHAN
	* "<="
	* LSQB
	* RSQB
	* STAR
	* CIRCUMFLEX
	* "=="

Previous tokens: Token('NAME', 'a')

  5. Describe What You’ve Tried

    Mention approaches you’ve already attempted to solve the problem.

  6. Be Patient and Respectful

    Remember that most help comes from volunteers. Be patient waiting for responses and respectful of people’s time.

Common Questions

Before asking, check if your question is answered in one of these resources:

Getting Involved

If you find yourself frequently answering questions about Formulate, consider getting more involved with the project:

  • Help improve the documentation

  • Contribute code fixes

  • Join the development team

See the Contributing to Formulate page for more information on how to contribute.