Move StringArrayTypes to pygmt/_typing.py

Also improve docstring of strings_to_ctypes_array function to mention np.ndarray as supported input.

pygmt/_typing.py

@@ -2,7 +2,17 @@
 Type aliases for type hints.
 """
 
+import contextlib
+import importlib
+from collections.abc import Sequence
 from typing import Literal
 
+import numpy as np
+
 # Anchor codes
 AnchorCode = Literal["TL", "TC", "TR", "ML", "MC", "MR", "BL", "BC", "BR"]
+
+# String array types
+StringArrayTypes = Sequence[str] | np.ndarray
+with contextlib.suppress(ImportError):
+    StringArrayTypes |= importlib.import_module(name="pyarrow").StringArray

pygmt/clib/conversion.py

@@ -9,17 +9,9 @@
 import numpy as np
 import pandas as pd
 from packaging.version import Version
+from pygmt._typing import StringArrayTypes
 from pygmt.exceptions import GMTInvalidInput
 
-StringArrayTypes = Sequence[str] | np.ndarray
-
-try:
-    import pyarrow as pa
-
-    StringArrayTypes |= pa.StringArray
-except ImportError:
-    pa = None
-
 
 def dataarray_to_matrix(grid):
     """
@@ -292,13 +284,13 @@ def sequence_to_ctypes_array(
 
 def strings_to_ctypes_array(strings: StringArrayTypes) -> ctp.Array:
     """
-    Convert a sequence (e.g., a list) of strings or a pyarrow.StringArray into a ctypes
-    array.
+    Convert a sequence (e.g., a list) or numpy.ndarray of strings or a
+    pyarrow.StringArray into a ctypes array.
 
     Parameters
     ----------
     strings
-        A sequence of strings or a pyarrow.StringArray.
+        A sequence of strings, a numpy.ndarray of str dtype, or a pyarrow.StringArray.
 
     Returns
     -------

pygmt/clib/session.py

@@ -17,6 +17,7 @@
 import numpy as np
 import pandas as pd
 import xarray as xr
+from pygmt._typing import StringArrayTypes
 from pygmt.clib.conversion import (
     array_to_datetime,
     dataarray_to_matrix,
@@ -34,16 +35,6 @@
     tempfile_from_image,
 )
 
-StringArrayTypes = Sequence[str] | np.ndarray
-
-try:
-    import pyarrow as pa
-
-    StringArrayTypes |= pa.StringArray
-except ImportError:
-    pa = None
-
-
 FAMILIES = [
     "GMT_IS_DATASET",  # Entity is a data table
     "GMT_IS_GRID",  # Entity is a grid