RustPython · bschoenmaeckers · Apr 4, 2026 · Apr 5, 2026 · Apr 5, 2026 · Apr 5, 2026
diff --git a/.cspell.dict/cpython.txt b/.cspell.dict/cpython.txt
@@ -169,6 +169,7 @@ pybuilddir
 pycore
 pyinner
 pydecimal
+pyerrors
 Pyfunc
 pylifecycle
 pymain

diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
@@ -114,10 +114,15 @@ jobs:
         uses: ./.github/actions/install-macos-deps
 
       - name: run rust tests
-        run: cargo test --workspace ${{ env.WORKSPACE_EXCLUDES }} --features threading ${{ env.CARGO_ARGS }}
+        run: cargo test --workspace --exclude rustpython-capi ${{ env.WORKSPACE_EXCLUDES }} --features threading ${{ env.CARGO_ARGS }}
         env:
           INSTA_WORKSPACE_ROOT: ${{ github.workspace }}
 
+      - name: run c-api tests
+        working-directory: crates/capi
+        run: cargo test
+        if: runner.os != 'Windows'  # Requires pyo3 0.29+ on Windows
+
       - run: cargo doc --locked
         if: runner.os == 'Linux'
 

diff --git a/Cargo.lock b/Cargo.lock
diff --git a/Cargo.toml b/Cargo.toml
@@ -103,6 +103,7 @@ lto = "thin"
 
 [patch.crates-io]
 parking_lot_core = { git = "https://github.com/youknowone/parking_lot", branch = "rustpython" }
+pyo3-ffi = { git = "https://github.com/PyO3/pyo3" }
 # REDOX START, Uncomment when you want to compile/check with redoxer
 # REDOX END
 
@@ -256,7 +257,7 @@ pkcs8 = "0.10"
 proc-macro2 = "1.0.105"
 psm = "0.1"
 pymath = { version = "0.2.0", features = ["mul_add", "malachite-bigint", "complex"] }
-pyo3 = "0.28"
+pyo3 = { git = "https://github.com/PyO3/pyo3" }
 quote = "1.0.45"
 radium = "1.1.1"
 rand = "0.9"

diff --git a/Lib/test/test_ctypes/test_python_api.py b/Lib/test/test_ctypes/test_python_api.py
@@ -7,8 +7,6 @@
 
 
 class PythonAPITestCase(unittest.TestCase):
-    # TODO: RUSTPYTHON - requires pythonapi (Python C API)
-    @unittest.expectedFailure
     def test_PyBytes_FromStringAndSize(self):
         PyBytes_FromStringAndSize = pythonapi.PyBytes_FromStringAndSize
 

diff --git a/crates/capi/Cargo.toml b/crates/capi/Cargo.toml
@@ -12,12 +12,18 @@ license.workspace = true
 crate-type = ["cdylib", "rlib"]
 
 [dependencies]
-rustpython-vm = { workspace = true, features = ["threading"] }
+bitflags.workspace = true
+num-complex.workspace = true
+rustpython-vm = { workspace = true, features = ["threading", "compiler"] }
 rustpython-stdlib = {workspace = true, features = ["threading"] }
 
 [dev-dependencies]
 pyo3 = { workspace = true, features = ["auto-initialize", "abi3"] }
 
+[features]
+# Enable PyObject_CallMethodObjArgs variadic function, which is only available on nightly Rust.
+nightly = []
+
 [lints]
 workspace = true
 

diff --git a/crates/capi/capi_todo.md b/crates/capi/capi_todo.md
@@ -0,0 +1,213 @@
+# Unimplemented C API functions
+
+Mapping source: `pyo3-ffi/src/*.rs`, which mirrors the CPython header split used by the C API.
+
+## `abstract.h`
+
+RustPython C API target: `crates/capi/src/abstract_.rs`
+
+- `PyIter_Check`
+- `PyIter_NextItem`
+- `PyIter_Send`
+- `PyMapping_Items`
+- `PyMapping_Keys`
+- `PyMapping_Size`
+- `PyMapping_Values`
+- `PyNumber_Add`
+- `PyNumber_Lshift`
+- `PyNumber_Or`
+- `PyNumber_Rshift`
+- `PyNumber_Subtract`
+- `PyObject_GetIter`
+- `PyObject_Size`
+- `PySequence_Check`
+- `PySequence_Concat`
+- `PySequence_Count`
+- `PySequence_DelItem`
+- `PySequence_DelSlice`
+- `PySequence_GetItem`
+- `PySequence_GetSlice`
+- `PySequence_InPlaceConcat`
+- `PySequence_InPlaceRepeat`
+- `PySequence_Index`
+- `PySequence_List`
+- `PySequence_Repeat`
+- `PySequence_SetItem`
+- `PySequence_SetSlice`
+- `PySequence_Size`
+- `PySequence_Tuple`
+
+## `bytearrayobject.h`
+
+RustPython C API target: `crates/capi/src/bytearrayobject.rs` (not present yet)
+
+- `PyByteArray_AsString`
+- `PyByteArray_Check`
+- `PyByteArray_FromObject`
+- `PyByteArray_FromStringAndSize`
+- `PyByteArray_Resize`
+- `PyByteArray_Size`
+
+## `descrobject.h`
+
+RustPython C API target: `crates/capi/src/descrobject.rs` (not present yet)
+
+- `PyDictProxy_New`
+
+## `dictobject.h`
+
+RustPython C API target: `crates/capi/src/dictobject.rs`
+
+- `PyDict_Contains`
+- `PyDict_Copy`
+- `PyDict_DelItem`
+- `PyDict_Items`
+- `PyDict_Keys`
+- `PyDict_Merge`
+- `PyDict_MergeFromSeq2`
+- `PyDict_Update`
+- `PyDict_Values`
+
+## `genericaliasobject.h`
+
+RustPython C API target: `crates/capi/src/genericaliasobject.rs` (not present yet)
+
+- `Py_GenericAlias`
+
+## `import.h`
+
+RustPython C API target: `crates/capi/src/import.rs`
+
+- `PyImport_ExecCodeModuleEx`
+
+## `listobject.h`
+
+RustPython C API target: `crates/capi/src/listobject.rs`
+
+- `PyList_AsTuple`
+- `PyList_GetSlice`
+- `PyList_SetSlice`
+- `PyList_Sort`
+
+## `longobject.h`
+
+RustPython C API target: `crates/capi/src/longobject.rs`
+
+- `PyLong_AsUnsignedLongLongMask`
+
+## `modsupport.h`
+
+RustPython C API target: `crates/capi/src/modsupport.rs` (not present yet)
+
+- `PyModule_ExecDef`
+- `PyModule_FromDefAndSpec2`
+
+## `moduleobject.h`
+
+RustPython C API target: `crates/capi/src/moduleobject.rs`
+
+- `PyModule_GetFilenameObject`
+- `PyModule_NewObject`
+
+## `object.h`
+
+RustPython C API target: `crates/capi/src/object.rs`
+
+- `PyCallable_Check`
+- `PyObject_ClearWeakRefs`
+- `PyObject_Dir`
+- `PyObject_GenericGetAttr`
+- `PyObject_GetOptionalAttr`
+- `PyObject_RichCompare`
+- `PyType_GetModuleName`
+
+## `osmodule.h`
+
+RustPython C API target: `crates/capi/src/osmodule.rs` (not present yet)
+
+- `PyOS_FSPath`
+
+## `pybuffer.h`
+
+RustPython C API target: `crates/capi/src/pybuffer.rs` (not present yet)
+
+- `PyBuffer_FromContiguous`
+- `PyBuffer_GetPointer`
+- `PyBuffer_IsContiguous`
+- `PyBuffer_Release`
+- `PyBuffer_ToContiguous`
+- `PyObject_GetBuffer`
+
+## `pycapsule.h`
+
+RustPython C API target: `crates/capi/src/capsule.rs`
+
+- `PyCapsule_GetContext`
+- `PyCapsule_Import`
+- `PyCapsule_SetContext`
+- `PyCapsule_SetPointer`
+
+## `pyerrors.h`
+
+RustPython C API target: `crates/capi/src/pyerrors.rs`
+
+- `PyException_GetCause`
+- `PyException_GetContext`
+- `PyException_SetContext`
+- `PyUnicodeDecodeError_Create`
+
+## `pystate.h`
+
+RustPython C API target: `crates/capi/src/pystate.rs`
+
+- `PyInterpreterState_Get`
+- `PyInterpreterState_GetID`
+
+## `setobject.h`
+
+RustPython C API target: `crates/capi/src/setobject.rs` (not present yet)
+
+- `PyFrozenSet_Check`
+- `PyFrozenSet_New`
+- `PySet_Add`
+- `PySet_Check`
+- `PySet_Clear`
+- `PySet_Contains`
+- `PySet_Discard`
+- `PySet_New`
+- `PySet_Pop`
+- `PySet_Size`
+
+## `sliceobject.h`
+
+RustPython C API target: `crates/capi/src/sliceobject.rs` (not present yet)
+
+- `PySlice_AdjustIndices`
+- `PySlice_New`
+- `PySlice_Unpack`
+
+## `unicodeobject.h`
+
+RustPython C API target: `crates/capi/src/unicodeobject.rs`
+
+- `PyUnicode_AsUTF8String`
+- `PyUnicode_DecodeFSDefaultAndSize`
+- `PyUnicode_EncodeFSDefault`
+- `PyUnicode_FromEncodedObject`
+
+## `warnings.h`
+
+RustPython C API target: `crates/capi/src/warnings.rs` (not present yet)
+
+- `PyErr_WarnEx`
+- `PyErr_WarnExplicit`
+
+## `weakrefobject.h`
+
+RustPython C API target: `crates/capi/src/weakrefobject.rs` (not present yet)
+
+- `PyWeakref_CheckProxy`
+- `PyWeakref_CheckRef`
+- `PyWeakref_GetRef`
+- `PyWeakref_NewProxy`
+- `PyWeakref_NewRef`
diff --git a/crates/capi/pyo3-rustpython.config b/crates/capi/pyo3-rustpython.config
@@ -1,4 +1,4 @@
-implementation=CPython
+implementation=RustPython
 version=3.14
 shared=true
 abi3=true
-Original file line number
+Diff line change
@@ Expand Up / @@ -169,6 +169,7 @@ pybuilddir @@
     pycore
     pyinner
     pydecimal
+    pyerrors
     Pyfunc
     pylifecycle
     pymain
@@ Expand Down @@