feat: Series.hist

[camriddell]

What type of PR is this? (check all applicable)

• 💾 Refactor
• ✨ Feature
• 🐛 Bug Fix
• 🔧 Optimization
• 📝 Documentation
• ✅ Test
• 🐳 Other

Related issues

• Related issue [Enh]: Support for narwhals.Expr.hist #1561

Checklist

• Code follows style guide (ruff)
• Tests added
• Documented the changes

If you have comments or can explain your changes, please do so below

Narwhals Expressions do not yet allow one to return a DataFrame (or a struct), so .hist is only implemented at the Series level to be compliant with the rest of the API.

The PyArrow implementation can likely be streamlined a bit more, so a review on that section would be appreciated.

[MarcoGorelli]

wow, amazing!

.hist is only implemented at the Series level to be compliant with the rest of the API.

agree, good design decision here, I think it would be quite awkward to add Expr.hist because:

• struct dtype is not supported by default in pandas (and not at all in pandas pre 2.0. Maybe 1.5. But not before that)
• it's a length-changing expression which it doesn't make sense to aggregate (e.g. nw.col('a').unique().len() makes sense but nw.col('a').hist().struct.field('value').sum() doesn't seem useful..), so supporting this for pyspark / duckdb / ibis could be a real issue. Ibis does seem to have bucket but there's no examples and I have no idea what it does

Hi @mscolnick - just wanted to check that Series.hist would still be useful to you?

[FBruzzesi]

Thanks a ton @camriddell ! I left a couple of comments and will go through the arrow implementation in more details later today 🚀

[FBruzzesi]

We should use self.__native_namespace__() here as well in place of pandas. I can see that cudf has a cut function, as well as modin

[FBruzzesi]

These are now imported on the top of the file anyway

Suggested change

	import pyarrow as pa
	import pyarrow.compute as pc