Improve the public type hints

HISTORY.rst

@@ -71,6 +71,24 @@ History
     from the C ``Reader.metadata()`` has the ``UnicodeDecodeError`` as its
     cause.
 
+* Added ``maxminddb.Mode``, which the README already described.
+* Type checkers now reject a subscript of ``maxminddb.types.Record`` or
+  ``Primitive``, such as ``Record[str]``. The subscript still works at
+  runtime. Pull request by Adam Hitchcock. GitHub #464.
+
+* Type hints:
+
+  * ``Primitive`` includes ``bytearray``, which the C extension returns for
+    the ``bytes`` type.
+  * ``Reader.__iter__`` declares its item type.
+  * Added the ``StrOrBytesPath`` and ``DatabaseSource`` aliases to
+    ``maxminddb.types``.
+  * The ``maxminddb.extension.Reader`` stub accepts only a path, as the
+    extension does.
+  * ``MODE_FD`` accepts any object whose ``read()`` method returns ``bytes``,
+    such as a ``gzip.GzipFile``. ``maxminddb.types.SupportsRead`` describes
+    this type.
+
 3.2.0 (2026-09-10)
 ++++++++++++++++++
 

docs/index.rst

@@ -35,6 +35,24 @@ Database Reader
     :undoc-members:
     :show-inheritance:
 
+=====
+Types
+=====
+
+.. automodule:: maxminddb.types
+    :members:
+    :undoc-members:
+    :exclude-members: Primitive, Record
+
+.. The runtime values of these aliases contain AnyStr, so give the types that
+   type checkers see.
+
+.. autodata:: maxminddb.types.Primitive
+    :annotation: = str | bytes | bytearray | bool | float | int
+
+.. autodata:: maxminddb.types.Record
+    :annotation: = Primitive | RecordList | RecordDict
+
 ==================
 Indices and tables
 ==================

maxminddb/__init__.py

@@ -3,7 +3,7 @@
 from __future__ import annotations
 
 from importlib.metadata import version
-from typing import IO, TYPE_CHECKING, cast
+from typing import TYPE_CHECKING, cast
 
 from .const import (
     MODE_AUTO,
@@ -12,12 +12,13 @@
     MODE_MEMORY,
     MODE_MMAP,
     MODE_MMAP_EXT,
+    Mode,
 )
-from .decoder import InvalidDatabaseError
+from .errors import InvalidDatabaseError
 from .reader import Reader
 
 if TYPE_CHECKING:
-    import os
+    from .types import DatabaseSource
 
 try:
     from . import extension as _extension
@@ -33,13 +34,14 @@
     "MODE_MMAP",
     "MODE_MMAP_EXT",
     "InvalidDatabaseError",
+    "Mode",
     "Reader",
     "open_database",
 ]
 
 
 def open_database(
-    database: str | bytes | int | os.PathLike[str] | os.PathLike[bytes] | IO[bytes],
+    database: DatabaseSource,
     mode: int = MODE_AUTO,
 ) -> Reader:
     """Open a MaxMind DB database.
@@ -84,8 +86,9 @@ def open_database(
     # The C type exposes the same API as the Python Reader, so for type
     # checking purposes, pretend it is one. (Ideally this would be a subclass
     # of, or share a common parent class with, the Python Reader
-    # implementation.)
-    return cast("Reader", _extension.Reader(database, mode))
+    # implementation.) The extension accepts only a path. It raises TypeError
+    # for a file descriptor or a file object.
+    return cast("Reader", _extension.Reader(database, mode))  # type: ignore[arg-type]
 
 
 __version__ = version("maxminddb")

maxminddb/extension.pyi

@@ -2,12 +2,10 @@
 
 from collections.abc import Iterator
 from ipaddress import IPv4Address, IPv4Network, IPv6Address, IPv6Network
-from os import PathLike
-from typing import IO
 
 from typing_extensions import Self
 
-from maxminddb.types import Record
+from maxminddb.types import Record, StrOrBytesPath
 
 class Reader:
     """A C extension implementation of a reader for the MaxMind DB format.
@@ -19,14 +17,14 @@ class Reader:
 
     def __init__(
         self,
-        database: str | bytes | int | PathLike[str] | PathLike[bytes] | IO[bytes],
+        database: StrOrBytesPath,
         mode: int = ...,
     ) -> None:
         """Reader for the MaxMind DB file format.
 
         Arguments:
             database: A path to a valid MaxMind DB file such as a GeoIP database
-                      file, or a file descriptor in the case of MODE_FD.
+                      file.
             mode: mode to open the database with. The only supported modes are
                   MODE_AUTO and MODE_MMAP_EXT.
 
@@ -59,7 +57,7 @@ class Reader:
 
     def __iter__(self) -> Iterator[tuple[IPv4Network | IPv6Network, Record]]: ...
     def __enter__(self) -> Self: ...
-    def __exit__(self, *args) -> None: ...  # noqa: ANN002
+    def __exit__(self, *args: object) -> None: ...
 
 class Metadata:
     """Metadata for the MaxMind DB reader."""

maxminddb/file.py

@@ -51,7 +51,7 @@ def close(self) -> None:
         """Close file."""
         self._handle.close()
 
-    if hasattr(os, "pread"):  # type: ignore[attr-defined]
+    if hasattr(os, "pread"):
 
         def _read(self, buffersize: int, offset: int) -> bytes:
             """Read that uses pread."""

maxminddb/reader.py

@@ -11,7 +11,7 @@
 import ipaddress
 from dataclasses import dataclass
 from ipaddress import IPv4Address, IPv4Network, IPv6Address, IPv6Network
-from typing import IO, TYPE_CHECKING, Any
+from typing import TYPE_CHECKING, Any
 
 from maxminddb.const import MODE_AUTO, MODE_FD, MODE_FILE, MODE_MEMORY, MODE_MMAP
 from maxminddb.decoder import Decoder
@@ -20,11 +20,10 @@
 
 if TYPE_CHECKING:
     from collections.abc import Iterator
-    from os import PathLike
 
     from typing_extensions import Self
 
-    from maxminddb.types import Record, RecordDict
+    from maxminddb.types import DatabaseSource, Record, RecordDict
 
 _IPV4_MAX_NUM = 2**32
 _REOPENED = "Attempt to iterate over a reopened MaxMind DB. Create a new iterator."
@@ -58,7 +57,7 @@ class Reader:
 
     def __init__(
         self,
-        database: str | bytes | int | PathLike[str] | PathLike[bytes] | IO[bytes],
+        database: DatabaseSource,
         mode: int = MODE_AUTO,
     ) -> None:
         """Reader for the MaxMind DB file format.
@@ -95,7 +94,7 @@ def __init__(
 
     def _load(
         self,
-        database: str | bytes | int | PathLike[str] | PathLike[bytes] | IO[bytes],
+        database: DatabaseSource,
         mode: int,
     ) -> None:
         # TRY301 is suppressed because the handler only closes the buffer and
@@ -229,10 +228,12 @@ def get_with_prefix_len(
             return self._resolve_data_pointer(pointer), prefix_len
         return None, prefix_len
 
-    def __iter__(self) -> Iterator:
+    def __iter__(self) -> Iterator[tuple[IPv4Network | IPv6Network, Record]]:
         return self._iterate(self._generation)
 
-    def _iterate(self, generation: int) -> Iterator:
+    def _iterate(
+        self, generation: int
+    ) -> Iterator[tuple[IPv4Network | IPv6Network, Record]]:
         children = self._generate_children(0, 0, 0)
         while True:
             # Check before the walk resumes and reads more nodes, as the C
@@ -247,7 +248,12 @@ def _iterate(self, generation: int) -> Iterator:
                 return
             yield record
 
-    def _generate_children(self, node: int, depth: int, ip_acc: int) -> Iterator:
+    def _generate_children(
+        self,
+        node: int,
+        depth: int,
+        ip_acc: int,
+    ) -> Iterator[tuple[IPv4Network | IPv6Network, Record]]:
         node_count = self._node_count
         bits = self._address_bits
         if node > node_count:
@@ -344,7 +350,7 @@ def _resolve_data_pointer(self, pointer: int) -> Record:
 
     def _load_buffer(
         self,
-        database: str | bytes | int | PathLike[str] | PathLike[bytes] | IO[bytes],
+        database: DatabaseSource,
         mode: int = MODE_AUTO,
     ) -> str:
         filename: Any
@@ -393,7 +399,7 @@ def close(self) -> None:
 
         self.closed = True
 
-    def __exit__(self, *_) -> None:  # noqa: ANN002
+    def __exit__(self, *_: object) -> None:
         self.close()
 
     def __enter__(self) -> Self:

maxminddb/types.py

@@ -1,10 +1,17 @@
-"""Types representing database records."""
+"""Types for database records and database arguments."""
 
 from __future__ import annotations
 
-from typing import TypeAlias
+import os
+from typing import TYPE_CHECKING, AnyStr, Protocol, TypeAlias
 
-Primitive: TypeAlias = str | bytes | bool | float | int
+if TYPE_CHECKING:
+    Primitive: TypeAlias = str | bytes | bytearray | bool | float | int
+    """Primitive is a type for a scalar value in a database record."""
+else:
+    # Through AnyStr, a subscript such as Record[str] works at runtime, as in
+    # 3.2.0. Type checkers reject the subscript.
+    Primitive: TypeAlias = AnyStr | bytes | bytearray | bool | float | int
 
 RecordList: TypeAlias = list["Record"]
 """RecordList is a type for lists in a database record."""
@@ -13,3 +20,18 @@
 """RecordDict is a type for dicts in a database record."""
 
 Record: TypeAlias = Primitive | RecordList | RecordDict
+"""Record is a type for a value in a database record."""
+
+StrOrBytesPath: TypeAlias = str | bytes | os.PathLike[str] | os.PathLike[bytes]
+"""StrOrBytesPath is a type for a path to a database file."""
+
+
+class SupportsRead(Protocol):
+    """SupportsRead is a type for a binary file object for MODE_FD."""
+
+    def read(self) -> bytes:
+        """Return the remaining bytes."""
+
+
+DatabaseSource: TypeAlias = StrOrBytesPath | int | SupportsRead
+"""DatabaseSource is a type for the database argument of a reader."""

pyproject.toml

@@ -94,6 +94,11 @@ ignore = [
 "setup.py" = ["ALL"]
 "tests/*" = ["ANN201", "D"]
 
+[tool.mypy]
+# mypy 2 enables this by default. Without it, mypy 1 accepts bytearray as
+# bytes, and the bytearray check in tests/typing_test.py cannot fail.
+strict_bytes = true
+
 [tool.pytest.ini_options]
 # Use importlib mode to prevent pytest from adding the project root to sys.path.
 # This ensures tests import from the tox virtualenv's installed package (which includes

tests/reader_test.py

@@ -28,6 +28,7 @@
 except ImportError:
     maxminddb.extension = None  # type: ignore[assignment]
 
+import maxminddb.types
 from maxminddb import InvalidDatabaseError, open_database
 from maxminddb.const import (
     MODE_AUTO,
@@ -1418,6 +1419,17 @@ class TestExtensionReaderWithIPObjects(BaseTestReader):
         reader_class = maxminddb.extension.Reader
 
 
+class TestModule(unittest.TestCase):
+    def test_mode_is_exported(self) -> None:
+        self.assertIs(maxminddb.Mode, maxminddb.const.Mode)
+
+    def test_record_subscript_works_at_runtime(self) -> None:
+        # 3.2.0 accepted Record[str] at runtime. typing_test.py checks that
+        # type checkers reject it.
+        maxminddb.types.Record[str]  # type: ignore[misc, type-arg]
+        maxminddb.types.Primitive[bytes]  # type: ignore[misc, type-arg]
+
+
 @unittest.skipIf(
     not has_maxminddb_extension() and not os.environ.get("MM_FORCE_EXT_TESTS"),
     "No C extension module found. Skipping tests",

tests/typing_test.py

@@ -0,0 +1,52 @@
+# mypy: warn-unused-ignores
+"""Static type checks for the public API.
+
+mypy checks this file in the lint environment. The code does not run. Each
+type: ignore marks a line that must fail the type check.
+"""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    import gzip
+    import io
+    from ipaddress import IPv4Network, IPv6Network
+    from pathlib import Path
+
+    from typing_extensions import assert_type
+
+    import maxminddb
+    import maxminddb.extension
+    from maxminddb.types import Primitive, Record
+
+    reader = maxminddb.open_database("GeoIP2-City.mmdb")
+    assert_type(reader.get("1.1.1.1"), Record | None)
+    assert_type(reader.get_with_prefix_len("1.1.1.1"), tuple[Record | None, int])
+    for network, record in reader:
+        assert_type(network, IPv4Network | IPv6Network)
+        assert_type(record, Record)
+    assert_type(reader.metadata().search_tree_size, int)
+    with maxminddb.open_database(Path("GeoIP2-City.mmdb")) as path_reader:
+        assert_type(path_reader, maxminddb.Reader)
+
+    # Record includes the bytearray that the C extension returns for the
+    # bytes type.
+    value: Record = bytearray(b"\x00")
+
+    # A TypeVar in Primitive would give Record members of type Any. mypy
+    # rejects Record[str] even then, so only this check catches it.
+    def check_not_generic(primitive: Primitive[str]) -> None:  # type: ignore[type-arg]
+        pass
+
+    def check_mode_fd(gzip_file: gzip.GzipFile, text_file: io.TextIOWrapper) -> None:
+        maxminddb.open_database(gzip_file, maxminddb.Mode.FD)
+        maxminddb.open_database(text_file, maxminddb.Mode.FD)  # type: ignore[arg-type]
+
+    extension_reader = maxminddb.extension.Reader("GeoIP2-City.mmdb")
+    for network, record in extension_reader:
+        assert_type(network, IPv4Network | IPv6Network)
+        assert_type(record, Record)
+    assert_type(extension_reader.metadata().node_byte_size, int)
+    maxminddb.extension.Reader(3)  # type: ignore[arg-type]