Improve Python version compatibility

pyproject.toml

@@ -26,7 +26,7 @@ name = "crate"
 dynamic = ["version"]
 description = "CrateDB Python Client"
 authors = [{ name = "Crate.io", email = "office@crate.io" }]
-requires-python = ">=3.10"
+requires-python = ">=3.6"
 readme = "README.rst"
 license = "Apache-2.0"
 classifiers = [
@@ -35,6 +35,10 @@ classifiers = [
         "Operating System :: OS Independent",
         "Programming Language :: Python",
         "Programming Language :: Python :: 3",
+        "Programming Language :: Python :: 3.6",
+        "Programming Language :: Python :: 3.7",
+        "Programming Language :: Python :: 3.8",
+        "Programming Language :: Python :: 3.9",
         "Programming Language :: Python :: 3.10",
         "Programming Language :: Python :: 3.11",
         "Programming Language :: Python :: 3.12",
@@ -59,7 +63,7 @@ dependencies = [
 dev = [
     "backports.zoneinfo<1; python_version<'3.9'",
     "certifi",
-    "coverage",
+    "coverage<8",
     "mypy<1.20",
     "pytest<10",
     "pytz",

src/crate/client/cursor.py

@@ -221,6 +221,8 @@ def duration(self):
     def _convert_rows(self):
         """
         Iterate rows, apply type converters, and generate converted rows.
+
+        The converter is only supported on Python >= 3.10.
         """
         if not ("col_types" in self._result and self._result["col_types"]):
             raise ValueError(
@@ -238,7 +240,7 @@ def _convert_rows(self):
         for row in self._result["rows"]:
             yield [
                 convert(value)
-                for convert, value in zip(converters, row, strict=False)
+                for convert, value in zip(converters, row, strict=False)  # type: ignore[call-overload]
             ]
 
     @property

tests/client/test_cursor.py

@@ -20,6 +20,7 @@
 # software solely pursuant to the terms of the relevant commercial agreement.
 
 import datetime
+import sys
 from ipaddress import IPv4Address
 from unittest import mock
 
@@ -58,6 +59,9 @@ def test_cursor_fetch(mocked_connection):
         ]
 
 
+@pytest.mark.skipif(
+    sys.version_info < (3, 10), reason="Test needs Python >= 3.10"
+)
 def test_cursor_description(mocked_connection):
     cursor = mocked_connection.cursor()
     response = {
@@ -249,6 +253,9 @@ def test_execute_with_bulk_args(mocked_connection):
     mocked_connection.client.sql.assert_called_once_with(statement, None, [[1]])
 
 
+@pytest.mark.skipif(
+    sys.version_info < (3, 10), reason="Converter needs Python >= 3.10"
+)
 def test_execute_custom_converter(mocked_connection):
     """
     Verify that a custom converter is correctly applied when passed to a cursor.
@@ -299,6 +306,9 @@ def test_execute_custom_converter(mocked_connection):
         ]
 
 
+@pytest.mark.skipif(
+    sys.version_info < (3, 10), reason="Converter needs Python >= 3.10"
+)
 def test_execute_with_converter_and_invalid_data_type(mocked_connection):
     converter = DefaultTypeConverter()
 
@@ -323,6 +333,9 @@ def test_execute_with_converter_and_invalid_data_type(mocked_connection):
             assert e.exception.args == "999 is not a valid DataType"
 
 
+@pytest.mark.skipif(
+    sys.version_info < (3, 10), reason="Converter needs Python >= 3.10"
+)
 def test_execute_array_with_converter(mocked_connection):
     converter = DefaultTypeConverter()
     cursor = mocked_connection.cursor(converter=converter)
@@ -345,6 +358,9 @@ def test_execute_array_with_converter(mocked_connection):
         ]
 
 
+@pytest.mark.skipif(
+    sys.version_info < (3, 10), reason="Converter needs Python >= 3.10"
+)
 def test_execute_array_with_converter_invalid(mocked_connection):
     converter = DefaultTypeConverter()
     cursor = mocked_connection.cursor(converter=converter)
@@ -368,6 +384,9 @@ def test_execute_array_with_converter_invalid(mocked_connection):
             )
 
 
+@pytest.mark.skipif(
+    sys.version_info < (3, 10), reason="Converter needs Python >= 3.10"
+)
 def test_execute_nested_array_with_converter(mocked_connection):
     converter = DefaultTypeConverter()
     cursor = mocked_connection.cursor(converter=converter)
@@ -405,6 +424,9 @@ def test_execute_nested_array_with_converter(mocked_connection):
         ]
 
 
+@pytest.mark.skipif(
+    sys.version_info < (3, 10), reason="Converter needs Python >= 3.10"
+)
 def test_executemany_with_converter(mocked_connection):
     converter = DefaultTypeConverter()
     cursor = mocked_connection.cursor(converter=converter)
@@ -426,6 +448,9 @@ def test_executemany_with_converter(mocked_connection):
         assert result == []
 
 
+@pytest.mark.skipif(
+    sys.version_info < (3, 10), reason="Converter needs Python >= 3.10"
+)
 def test_execute_with_timezone(mocked_connection):
     # Create a `Cursor` object with `time_zone`.
     tz_mst = datetime.timezone(datetime.timedelta(hours=7), name="MST")

tests/client/tests.py

@@ -1,4 +1,5 @@
 import doctest
+import sys
 import unittest
 
 from .layer import (
@@ -18,14 +19,17 @@ def test_suite():
     suite.addTest(doctest.DocTestSuite("crate.client.connection"))
     suite.addTest(doctest.DocTestSuite("crate.client.http"))
 
-    s = doctest.DocFileSuite(
-        "docs/by-example/connection.rst",
-        "docs/by-example/cursor.rst",
-        module_relative=False,
-        optionflags=flags,
-        encoding="utf-8",
-    )
-    suite.addTest(s)
+    if sys.version_info >= (3, 10):
+        # This suite includes converter tests,
+        # which are only available with Python 3.10 and newer.
+        s = doctest.DocFileSuite(
+            "docs/by-example/connection.rst",
+            "docs/by-example/cursor.rst",
+            module_relative=False,
+            optionflags=flags,
+            encoding="utf-8",
+        )
+        suite.addTest(s)
 
     s = doctest.DocFileSuite(
         "docs/by-example/https.rst",