feat: Add `is_into_lazyframe`, export missing functionalities, fix SQLFrame bug by FBruzzesi · Pull Request #3613 · narwhals-dev/narwhals

FBruzzesi · 2026-05-11T23:20:20Z

Description

Small late night rant: everything always turn out bigger than what it looks like. End of rant

As per title

Introduces is_into_lazyframe
Exports missing functionalities from dependencies modules
Fixes SQLFrame bug (currently is_into_lazyframe(sqlframe_object) -> True
Improves _warn_if_narwhals_* by getting the calling function name via caller = sys._getframe(1).f_code.co_name and replace is_pandas_dataframe hardcoded value

@dangotbanned I read your comment in #3612 when I was already down this rabbit hole 😭

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

Related issues

Closes feat: Add is_into_lazyframe #3612
Related Add type guard for what from_native supports #3530

FBruzzesi · 2026-05-12T17:17:57Z

downstream marimo is affected. I will investigate later today

FBruzzesi · 2026-05-12T20:02:47Z

+
+def is_into_dataframe(native_dataframe: Any | IntoDataFrameT) -> TypeIs[IntoDataFrameT]:
+    """Check whether `native_dataframe` can be converted to a narwhals.stable.v1.DataFrame."""
+    from narwhals.stable.v1 import DataFrame


Thoughts on pulling DataFrame from v1 here? Should we do the same for v2?

I'm not sure actually.

Usually I'd say yes, but from_native converts between versions now. So maybe there's not a benefit to the version distinction?

…narwhals/pull/3613\#discussion_r3229405470

related #3613 (comment)

dangotbanned

Thanks @FBruzzesi

I've not got much, but it's honest work 🙂

dangotbanned · 2026-05-13T21:49:42Z

+    if is_narwhals_dataframe(frame) or is_narwhals_lazyframe(frame):
+        from narwhals._utils import qualified_type_name
+
+        caller = sys._getframe(1).f_code.co_name


Well aren't you a fancy boi 😄

dangotbanned

Thanks again for taking things on board, here's round 2

dangotbanned

Thanks @FBruzzesi for powering through this

MarcoGorelli · 2026-05-22T12:48:13Z

+        or is_ibis_table(native_dataframe)
+        or is_duckdb_relation(native_dataframe)


i'm confused, doesn't the docstring say that these aren't accepted here?

🤨

narwhals/src/narwhals/stable/v1/dependencies.py

Line 68 in aa04980

`ibis` tables and `duckdb` relations are treated as DataFrames here, since

well it says

arbitrary objects implementing the __dataframe__ interchange
protocol narwhals.stable.v1.typing.DataFrameLike are accepted
by v1.from_native(..., eager_or_interchange_only=True) but are not
recognised by this function

so why are they being special-cased?

based on the previous thread, i thought we were preseving v1 behaviour for is_into_dataframe

I thought we were on the same page to fix the example in #3613 (comment)

import narwhals.stable.v1 as nw nw.dependencies.is_into_dataframe(duckdb_obj) # False isinstance(nw.from_native(duckdb_obj), nw.DataFrame) # True

this requires to change is_into_dataframe runtime behavior for ibis and duckdb

Yeah I was thinking the same.

The issue was with dask and __dataframe__.

I'm not sure what the purpose of a v1 is_into_dataframe is if it can't test any of the unique types it describes?

narwhals/narwhals/stable/v1/typing.py

Lines 28 to 29 in 98b4c8c

IntoDataFrame: TypeAlias = Union["NativeDataFrame", "DataFrameLike", "NativeDuckDB"]

"""Anything which can be converted to a Narwhals DataFrame.

sorry i wasn't clear

if there's no need to change it, i'd prefer to keep existing behaviour than to modify anything in v1

(and if it did need changing, it should be a separate pr labelled as bug fix)

I understand the feeling of

if there's no need to change it, i'd prefer to keep existing behaviour than to modify anything in v1

yet to me this seems like a clear bug. Since we are touching every dependency file anyway, I thought to address it.

(and if it did need changing, it should be a separate pr labelled as bug fix)

In my defence the PR always had both enhancement and fix labels, and my first self comment was exactly on this very change to bring the focus on it #3613 (comment)

true, thanks for looking into it. if it's ok, i'd still prefer to leave as-is, i'm concerned about unforeseen knock-on effects here not captured by ci or downstream tests

also true 🙌 but from a "do we need to revert this?" perspective, it's much easier if it's separate

FBruzzesi · 2026-05-22T16:39:17Z

+# TODO(Unassigned): For duckdb and ibis backends:
+#   * is_into_dataframe(native_frame) returns False
+#   * nw_v1.from_native(native_frame) returns a narwhals.stable.v1.DataFrame
+#   * Therefore is_into_dataframe(nw_v1.from_native(native_frame)) returns True
+# See discussion https://github.com/narwhals-dev/narwhals/pull/3613#discussion_r3288440039


@MarcoGorelli I added this comment to track the behavior after rolling back the changes

FBruzzesi added 4 commits May 12, 2026 00:26

feat: Add is_into_lazyframe

9a72f99

fixup warnings

22e979a

main and v1 dependencies fixes

b613345

unit tests and sqlframe issue

db4aa27

FBruzzesi requested a review from dangotbanned May 11, 2026 23:20

FBruzzesi added enhancement New feature or request fix labels May 11, 2026

FBruzzesi commented May 11, 2026

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Comment thread src/narwhals/stable/v1/dependencies.py Outdated

FBruzzesi commented May 11, 2026

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Comment thread narwhals/dependencies.py Outdated

FBruzzesi and others added 2 commits May 12, 2026 01:43

fix import, fix unit tests

fd75a8b

Merge branch 'main' into feat/is_into_lazyframe

9b95b9b

FBruzzesi commented May 12, 2026

View reviewed changes

FBruzzesi and others added 2 commits May 12, 2026 23:04

Align v2 behaviour, resolve comment: https://github.com/narwhals-dev/…

74e2164

…narwhals/pull/3613\#discussion_r3229405470

fix: Avoid hasattr false-positives

e1aeff5

related #3613 (comment)

dangotbanned reviewed May 13, 2026

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FBruzzesi added 4 commits May 14, 2026 09:27

Use _hasattr_static in all is_into_*

95287e6

merge main

aa8bac6

refactor(perf): Do not check isinstance per each nested call

35d0b88

simplify by aliasing

98b4c8c

dangotbanned self-requested a review May 15, 2026 08:48

dangotbanned reviewed May 15, 2026

View reviewed changes

Comment thread src/narwhals/stable/v1/dependencies.py Outdated

Comment thread tests/dependencies/is_into_dataframe_test.py

Comment thread tests/dependencies/is_into_lazyframe_test.py Outdated

Comment thread tests/dependencies/is_into_dataframe_test.py Outdated

dangotbanned mentioned this pull request May 15, 2026

Add type guard for what from_native supports #3530

Open

FBruzzesi added 4 commits May 16, 2026 09:55

fix up is_into_*_test typing

7625405

Add DynamicAttrOnly tests

c6b4d6f

**not** is_into_series(dynamic_attr_only)

3247238

no cover DynamicAttrOnly.__getattr__

8495ffd

FBruzzesi commented May 16, 2026

View reviewed changes

Comment thread tests/dependencies/conftest.py Outdated

FBruzzesi requested a review from dangotbanned May 16, 2026 08:57

merge main, solve conflicts

bce6fdb

FBruzzesi and others added 4 commits May 16, 2026 22:42

rename: DynamicAttrOnly -> AlwaysHasAttr

efaa06b

Merge branch 'main' into feat/is_into_lazyframe

f45f6ce

Merge branch 'main' into feat/is_into_lazyframe

d1a256c

Discussion summarizing note

cc294dd

dangotbanned reviewed May 21, 2026

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Comment thread src/narwhals/stable/v1/dependencies.py Outdated

dangotbanned reviewed May 21, 2026

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Comment thread src/narwhals/dependencies.py Outdated

FBruzzesi added 2 commits May 22, 2026 10:13

docs: Remove links

a7de868

rm warning in 'is_into_<narwhals_obj>'

aa04980

dangotbanned approved these changes May 22, 2026

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MarcoGorelli requested changes May 22, 2026

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Rollback v1 changes

79b0aa9

FBruzzesi commented May 22, 2026

View reviewed changes

merge main

fc4a4f1

		or is_ibis_table(native_dataframe)
		or is_duckdb_relation(native_dataframe)

	IntoDataFrame: TypeAlias = Union["NativeDataFrame", "DataFrameLike", "NativeDuckDB"]
	"""Anything which can be converted to a Narwhals DataFrame.

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FBruzzesi commented May 11, 2026 • edited by dangotbanned Loading Uh oh! There was an error while loading. Please reload this page.

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FBruzzesi commented May 12, 2026

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MarcoGorelli May 22, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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FBruzzesi commented May 11, 2026 •

edited by dangotbanned

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MarcoGorelli May 22, 2026 •

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