fix compatibility with pandas 3 (#747)

Co-authored-by: Christopher Rowley <github.com/cjdoris>

Author: cjdoris

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Unreleased
 * Added `juliacall.TypeValue.__numpy_dtype__` attribute to allow converting Julia types
   to the corresponding NumPy dtype, like `numpy.dtype(jl.Int)`.
+* Bug fixes.
 
 ## 0.9.31 (2025-12-17)
 * Restore support for Python 3.14+.

CondaPkg.toml

@@ -16,3 +16,4 @@ version = ">=3.10,!=3.14.0,!=3.14.1,<4"
 matplotlib = ""
 numpy = ""
 pyside6 = ""
+pandas = ""

src/Wrap/Wrap.jl

@@ -55,18 +55,22 @@ function __init__()
     pyconvert_add_rule("collections.abc:Mapping", PyDict, pyconvert_rule_mapping, priority)
     pyconvert_add_rule("io:IOBase", PyIO, pyconvert_rule_io, priority)
     pyconvert_add_rule("_io:_IOBase", PyIO, pyconvert_rule_io, priority)
-    pyconvert_add_rule(
-        "pandas.core.frame:DataFrame",
-        PyPandasDataFrame,
-        pyconvert_rule_pandasdataframe,
-        priority,
-    )
-    pyconvert_add_rule(
-        "pandas.core.arrays.base:ExtensionArray",
-        PyList,
-        pyconvert_rule_sequence,
-        priority,
-    )
+    for typename in ["pandas.core.frame:DataFrame", "pandas:DataFrame"]
+        pyconvert_add_rule(
+            typename,
+            PyPandasDataFrame,
+            pyconvert_rule_pandasdataframe,
+            priority,
+        )
+    end
+    for typename in ["pandas.core.arrays.base:ExtensionArray", "pandas.api.extensions:ExtensionArray"]
+        pyconvert_add_rule(
+            typename,
+            PyList,
+            pyconvert_rule_sequence,
+            priority,
+        )
+    end
 
     priority = PYCONVERT_PRIORITY_NORMAL
     pyconvert_add_rule("<arraystruct>", Array, pyconvert_rule_array, priority)

test/Compat.jl

@@ -104,12 +104,14 @@ end
     end
 end
 
-@testitem "Tables.jl" begin
+@testitem "Tables.jl" setup=[Setup] begin
     @testset "pytable" begin
         x = (x = [1, 2, 3], y = ["a", "b", "c"])
         # pandas
-        # TODO: install pandas and test properly
-        @test_throws PyException pytable(x, :pandas)
+        if Setup.devdeps
+            y = pytable(x, :pandas)
+            @test pyeq(Bool, pytype(y), pyimport("pandas").DataFrame)
+        end
         # columns
         y = pytable(x, :columns)
         @test pyeq(Bool, y, pydict(x = [1, 2, 3], y = ["a", "b", "c"]))

test/Convert.jl

@@ -305,6 +305,19 @@ end
     @test_throws Exception pyconvert(Second, td(microseconds = 1000))
 end
 
+@testitem "pandas.DataFrame → PyPandasDataFrame" setup=[Setup] begin
+    if Setup.devdeps
+        pd = pyimport("pandas")
+        df = pd.DataFrame()
+        df2 = pyconvert(PyPandasDataFrame, df)
+        @test df2 isa PyPandasDataFrame
+        @test pyis(df2, df)
+        df3 = pyconvert(PyTable, df)
+        @test df3 isa PyPandasDataFrame
+        @test pyis(df3, df)
+    end
+end
+
 @testitem "pyconvert_add_rule (#364)" begin
     id = string(rand(UInt128), base = 16)
     pyexec(

test/Wrap.jl

@@ -458,26 +458,23 @@ end
     end
 end
 
-@testitem "PyPandasDataFrame" begin
+@testitem "PyPandasDataFrame" setup=[Setup] begin
     using Tables
     @test PyPandasDataFrame isa Type
-    # TODO: figure out how to get pandas into the test environment
-    # for now use some dummy type and take advantage of the fact that the code doesn't actually check it's a real dataframe
-    @pyexec """
-    class DataFrame:
-        def __init__(self, **kw):
-            self.__dict__.update(kw)
-    """ => DataFrame
-    df = DataFrame(shape = (4, 3), columns = pylist(["foo", "bar", "baz"]))
-    x = PyPandasDataFrame(df)
-    @test ispy(x)
-    @test Py(x) === df
-    @test Tables.istable(x)
-    @test Tables.columnaccess(x)
-    @test_throws Exception Tables.columns(x)
-    @test_throws Exception pyconvert(PyPandasDataFrame, 1)
-    str = sprint(show, MIME("text/plain"), x)
-    @test occursin(r"4×3 .*PyPandasDataFrame", str)
+    if Setup.devdeps
+        pd = pyimport("pandas")
+        df = pd.DataFrame(pydict(foo=pylist([1,2,3,4]), bar=pylist([2,3,4,5]), baz=pylist([3,4,5,6])))
+        x = PyPandasDataFrame(df)
+        @test ispy(x)
+        @test Py(x) === df
+        @test Tables.istable(x)
+        @test Tables.columnaccess(x)
+        # TODO: test the tables interface more fully
+        Tables.columns(x)
+        @test_throws Exception pyconvert(PyPandasDataFrame, 1)
+        str = sprint(show, MIME("text/plain"), x)
+        @test occursin(r"4×3 .*PyPandasDataFrame", str)
+    end
 end
 
 @testitem "PySet" begin