gnu: python-pandarallel: Fix build.

* gnu/packages/patches/python-pandarallel-fix-df-applymap.patch: Add
patch.
* gnu/packages/patches/python-pandarallel-fix-parallel_apply.patch:
Likewise.
* gnu/local.mk (dist_patch_DATA): Record patches.
* gnu/packages/python-science.scm (python-pandarallel)
[source]{patches}: Record them.

Signed-off-by: Andreas Enge <andreas@enge.fr>

4 files changed, 133 insertions, 1 deletions

diff --git a/gnu/local.mk b/gnu/local.mk
index f227c550e3a..f78ab43ca1a 100644
--- a/gnu/local.mk
+++ b/gnu/local.mk
@@ -2300,6 +2300,8 @@ dist_patch_DATA =						\
   %D%/packages/patches/python-mslice-matplotlib-3.6-compatibility.patch \
   %D%/packages/patches/python-packaging-test-arch.patch         \
   %D%/packages/patches/python-pandas-2-no-pytz_datetime.patch           \
+  %D%/packages/patches/python-pandarallel-fix-df-applymap.patch         \
+  %D%/packages/patches/python-pandarallel-fix-parallel_apply.patch              \
   %D%/packages/patches/python-property-cached-asyncio-3_11.patch        \
   %D%/packages/patches/python-pyan3-fix-absolute-path-bug.patch \
   %D%/packages/patches/python-pyan3-fix-positional-arguments.patch \
diff --git a/gnu/packages/patches/python-pandarallel-fix-df-applymap.patch b/gnu/packages/patches/python-pandarallel-fix-df-applymap.patch
new file mode 100644
index 00000000000..8aef98a03fc
--- /dev/null
+++ b/gnu/packages/patches/python-pandarallel-fix-df-applymap.patch
@@ -0,0 +1,48 @@
+From f4e59d5a12d10b87d55f91e195ec4b8064fa66ca Mon Sep 17 00:00:00 2001
+From: goosfrabba <16498111+goosfrabba@users.noreply.github.com>
+Date: Mon, 6 Jul 2026 10:58:21 -0700
+Subject: [PATCH] Fix DataFrame.applymap deprecation on pandas >= 2.1 without
+ dropping pandas < 2.1
+
+pandas >= 2.1 deprecates DataFrame.applymap in favour of DataFrame.map, so parallel_applymap
+raises a FutureWarning (#258). ApplyMap.work now uses DataFrame.map when the installed pandas
+provides it and falls back to applymap otherwise, fixing the deprecation without dropping
+pandas < 2.1 or bumping the minimum Python version (the concern raised on #259). The reference
+computation in test_dataframe_applymap uses the same capability check so it stays warning-free.
+---
+ pandarallel/data_types/dataframe.py | 6 ++++++
+ tests/test_pandarallel.py           | 4 +++-
+ 2 files changed, 9 insertions(+), 1 deletion(-)
+
+diff --git a/pandarallel/data_types/dataframe.py b/pandarallel/data_types/dataframe.py
+index 29c7e50..e1bc627 100644
+--- a/pandarallel/data_types/dataframe.py
++++ b/pandarallel/data_types/dataframe.py
+@@ -66,6 +66,12 @@ def work(
+             user_defined_function_kwargs: Dict[str, Any],
+             extra: Dict[str, Any],
+         ) -> pd.DataFrame:
++            # pandas >= 2.1 deprecates DataFrame.applymap in favour of DataFrame.map (added in 2.1);
++            # older pandas only has applymap. Use whichever this pandas provides, so elementwise
++            # apply keeps working and no longer raises the FutureWarning reported in #258, without
++            # dropping support for pandas < 2.1.
++            if hasattr(data, "map"):
++                return data.map(user_defined_function)
+             return data.applymap(user_defined_function)
+ 
+         @staticmethod
+diff --git a/tests/test_pandarallel.py b/tests/test_pandarallel.py
+index 0f91c32..567c7d5 100644
+--- a/tests/test_pandarallel.py
++++ b/tests/test_pandarallel.py
+@@ -232,7 +232,9 @@ def test_dataframe_applymap(pandarallel_init, func_dataframe_applymap, df_size):
+     )
+     df.index = [item / 10 for item in df.index]
+ 
+-    res = df.applymap(func_dataframe_applymap)
++    # pandas >= 2.1 renamed DataFrame.applymap to DataFrame.map; use whichever this pandas
++    # provides so the reference computation stays warning-free across versions.
++    res = (df.map if hasattr(df, "map") else df.applymap)(func_dataframe_applymap)
+     res_parallel = df.parallel_applymap(func_dataframe_applymap)
+     assert res.equals(res_parallel)
+ 
diff --git a/gnu/packages/patches/python-pandarallel-fix-parallel_apply.patch b/gnu/packages/patches/python-pandarallel-fix-parallel_apply.patch
new file mode 100644
index 00000000000..2d58cbf6482
--- /dev/null
+++ b/gnu/packages/patches/python-pandarallel-fix-parallel_apply.patch
@@ -0,0 +1,79 @@
+From cebc07fed0707457487656836e627a154416d252 Mon Sep 17 00:00:00 2001
+From: Palash Lalwani <palashlalwani.r@gmail.com>
+Date: Wed, 22 Jul 2026 21:24:52 +0530
+Subject: [PATCH] fix: don't pass grouping columns to
+ groupby().parallel_apply() on pandas >= 3.0
+
+Since pandas 3.0, DataFrameGroupBy.apply operates on _obj_with_exclusions, so the
+grouping columns are no longer passed to the applied function. Iterating a
+DataFrameGroupBy still yields them, which is how pandarallel builds its chunks, so
+parallel_apply kept passing them.
+
+This produced a silent divergence rather than an error: user functions that iterate
+columns or aggregate across the frame got different results from parallel_apply than
+from apply.
+
+Restrict each group to the columns apply would have used, gated on the pandas version
+so behaviour on pandas < 3.0 is unchanged.
+
+The groupby test fixture read df.b, but the test also covers groupby(["a", "b"]) where
+b is now a grouping column, making the reference apply() call raise on pandas 3.0.
+Switched the fixture to column c, which is never a grouping column in these tests.
+---
+ pandarallel/data_types/dataframe_groupby.py | 18 +++++++++++++++++-
+ tests/test_pandarallel.py                   |  8 ++++++--
+ 2 files changed, 23 insertions(+), 3 deletions(-)
+
+diff --git a/pandarallel/data_types/dataframe_groupby.py b/pandarallel/data_types/dataframe_groupby.py
+index f2dbb91..9b448d7 100644
+--- a/pandarallel/data_types/dataframe_groupby.py
++++ b/pandarallel/data_types/dataframe_groupby.py
+@@ -17,8 +17,24 @@ def get_chunks(
+             chunks = chunk(dataframe_groupby.ngroups, nb_workers)
+             iterator = iter(dataframe_groupby)
+ 
++            # Since pandas 3.0, `DataFrameGroupBy.apply` operates on
++            # `_obj_with_exclusions`, i.e. the grouping columns are no longer passed to
++            # the applied function. Iterating a `DataFrameGroupBy` still yields them
++            # though, so restrict each group to the columns `apply` would have used.
++            # On pandas < 3.0 the grouping columns are still passed, so keep them.
++            columns = (
++                dataframe_groupby._obj_with_exclusions.columns
++                if get_pandas_version() >= (3, 0)
++                else None
++            )
++
+             for chunk_ in chunks:
+-                yield [next(iterator) for _ in range(chunk_.stop - chunk_.start)]
++                groups = [next(iterator) for _ in range(chunk_.stop - chunk_.start)]
++
++                if columns is not None:
++                    groups = [(key, df[columns]) for key, df in groups]
++
++                yield groups
+ 
+         @staticmethod
+         def work(
+diff --git a/tests/test_pandarallel.py b/tests/test_pandarallel.py
+index 0f91c32..2f43458 100644
+--- a/tests/test_pandarallel.py
++++ b/tests/test_pandarallel.py
+@@ -93,12 +93,16 @@ def func(x):
+ 
+ @pytest.fixture()
+ def func_dataframe_groupby_apply():
++    # Uses column `c`, which is never a grouping column in the tests below. Since pandas
++    # 3.0 the grouping columns are not passed to the applied function, so a function
++    # reading `df.b` would fail on the `groupby(["a", "b"])` case before `parallel_apply`
++    # is even reached.
+     def func(df):
+         dum = 0
+-        for item in df.b:
++        for item in df.c:
+             dum += math.log10(math.sqrt(math.exp(item**2)))
+ 
+-        return dum / len(df.b)
++        return dum / len(df.c)
+ 
+     return func
+ 
diff --git a/gnu/packages/python-science.scm b/gnu/packages/python-science.scm
index 9389d849c11..0ab894aecbf 100644
--- a/gnu/packages/python-science.scm
+++ b/gnu/packages/python-science.scm
@@ -4649,7 +4649,10 @@ convention of suggesting best recommended practices for using
              (commit (string-append "v" version))))
        (file-name (git-file-name name version))
        (sha256
-        (base32 "0r2wlxlwp4wia0vm15k4cp421mwa20k4k5g2ml01inprj8bl1p0p"))))
+        (base32 "0r2wlxlwp4wia0vm15k4cp421mwa20k4k5g2ml01inprj8bl1p0p"))
+       (patches
+        (search-patches "python-pandarallel-fix-df-applymap.patch"
+                        "python-pandarallel-fix-parallel_apply.patch"))))
     (build-system pyproject-build-system)
     (arguments
      (list