Add flake8-type-checking extension

py-polars/.flake8

@@ -1,5 +1,6 @@
 [flake8]
 max-line-length = 88
+type-checking-exempt-modules = typing_extensions
 docstring-convention=all
 extend-ignore =
     # Satisfy black: https://black.readthedocs.io/en/stable/guides/using_black_with_other_tools.html#flake8
@@ -11,6 +12,8 @@ extend-ignore =
     D1, D400, D205,
     # flake8-simplify
     SIM102, SIM117,
+    # flake8-type-checking
+    TC006,
 
 per-file-ignores =
     __init__.py:F401

py-polars/build.requirements.txt

@@ -24,6 +24,7 @@ flake8-bugbear==22.7.1
 flake8-comprehensions==3.10.0
 flake8-docstrings==1.6.0
 flake8-simplify==0.19.3
+flake8-type-checking==2.1.0
 sphinx==4.2.0
 pydata-sphinx-theme==0.6.3
 sphinx-panels==0.6.0

py-polars/polars/_html.py

@@ -3,11 +3,13 @@
 
 import os
 from textwrap import dedent
-from types import TracebackType
-from typing import Iterable
+from typing import TYPE_CHECKING, Iterable
 
 from polars.datatypes import Object
 
+if TYPE_CHECKING:
+    from types import TracebackType
+
 
 class Tag:
     """Class for representing an HTML tag."""

py-polars/polars/datatypes.py

@@ -3,7 +3,7 @@
 import ctypes
 import sys
 from datetime import date, datetime, time, timedelta
-from typing import Any, Dict, Optional, Sequence, Tuple, Type, Union
+from typing import TYPE_CHECKING, Any, Dict, Optional, Sequence, Tuple, Type, Union
 
 try:
     import pyarrow as pa
@@ -12,7 +12,6 @@
 except ImportError:
     _PYARROW_AVAILABLE = False
 
-from _ctypes import _SimpleCData  # type: ignore[import]
 
 try:
     from polars.polars import dtype_str_repr
@@ -22,6 +21,9 @@
 except ImportError:
     _DOCUMENTING = True
 
+if TYPE_CHECKING:
+    from _ctypes import _SimpleCData  # type: ignore[import]
+
 
 def get_idx_type() -> Type[DataType]:
     """

py-polars/polars/internals/datatypes.py

@@ -1,7 +1,8 @@
 from __future__ import annotations
 
-from typing import Union
+from typing import TYPE_CHECKING, Union
 
-from polars import internals as pli
+if TYPE_CHECKING:
+    from polars import internals as pli
 
 IntoExpr = Union[int, float, str, "pli.Expr", "pli.Series"]

py-polars/polars/internals/expr.py

@@ -4,7 +4,7 @@
 import math
 import random
 from datetime import date, datetime, timedelta
-from typing import Any, Callable, List, Sequence
+from typing import TYPE_CHECKING, Any, Callable, List, Sequence
 
 from polars import internals as pli
 from polars.datatypes import (
@@ -21,20 +21,16 @@
 )
 from polars.utils import _timedelta_to_pl_duration
 
-try:
-    from polars.polars import PyExpr
-
-    _DOCUMENTING = False
-except ImportError:
-    _DOCUMENTING = True
-
 try:
     import numpy as np
 
     _NUMPY_AVAILABLE = True
 except ImportError:
     _NUMPY_AVAILABLE = False
 
+if TYPE_CHECKING:
+    from polars.polars import PyExpr
+
 
 def selection_to_pyexpr_list(
     exprs: str | Expr | Sequence[str | Expr | pli.Series] | pli.Series,

py-polars/polars/internals/io.py

@@ -4,10 +4,17 @@
 from contextlib import contextmanager
 from io import BytesIO, StringIO
 from pathlib import Path
-from typing import Any, BinaryIO, ContextManager, Iterator, TextIO, overload
+from typing import (
+    TYPE_CHECKING,
+    Any,
+    BinaryIO,
+    ContextManager,
+    Iterator,
+    TextIO,
+    overload,
+)
 from urllib.request import urlopen
 
-from polars.datatypes import DataType
 from polars.utils import format_path
 
 try:
@@ -24,6 +31,9 @@
 except ImportError:
     pass
 
+if TYPE_CHECKING:
+    from polars.datatypes import DataType
+
 
 def _process_http_file(path: str) -> BytesIO:
     with urlopen(path) as f:

py-polars/polars/string_cache.py

@@ -1,6 +1,6 @@
 from __future__ import annotations
 
-from types import TracebackType
+from typing import TYPE_CHECKING
 
 try:
     from polars.polars import toggle_string_cache as pytoggle_string_cache
@@ -9,6 +9,9 @@
 except ImportError:
     _DOCUMENTING = True
 
+if TYPE_CHECKING:
+    from types import TracebackType
+
 
 class StringCache:
     """

py-polars/polars/utils.py

@@ -7,8 +7,7 @@
 import sys
 import warnings
 from datetime import date, datetime, time, timedelta, timezone
-from pathlib import Path
-from typing import Any, Callable, Iterable, Sequence
+from typing import TYPE_CHECKING, Any, Callable, Iterable, Sequence
 
 from polars.datatypes import DataType, Date, Datetime
 
@@ -31,6 +30,9 @@
 else:
     from typing_extensions import TypeGuard
 
+if TYPE_CHECKING:
+    from pathlib import Path
+
 
 def _process_null_values(
     null_values: None | str | list[str] | dict[str, str] = None,

py-polars/tests/io/test_csv.py

@@ -7,13 +7,16 @@
 import zlib
 from datetime import date
 from pathlib import Path
+from typing import TYPE_CHECKING
 
 import pytest
 
 import polars as pl
-from polars import DataType
 from polars.testing import assert_frame_equal_local_categoricals
 
+if TYPE_CHECKING:
+    from polars import DataType
+
 
 def test_quoted_date() -> None:
     csv = textwrap.dedent(

py-polars/tests/test_lazy.py

@@ -1,13 +1,17 @@
 from __future__ import annotations
 
+from typing import TYPE_CHECKING
+
 import numpy as np
 import pytest
-from _pytest.capture import CaptureFixture
 
 import polars as pl
 from polars import col, lit, map_binary, when
 from polars.testing import assert_frame_equal
 
+if TYPE_CHECKING:
+    from _pytest.capture import CaptureFixture
+
 
 def test_lazy() -> None:
     df = pl.DataFrame({"a": [1, 2, 3], "b": [1.0, 2.0, 3.0]})