Repository: great-expectations/great_expectations

Issue:
Use cleaner solution for non-truncating division in python 2
Prefer `from __future__ import division` to `1.*x/y`


Discussion:
Done inline during improve_partitions push.

Resolving patch:
diff --git a/contrib/experimental/great_expectations_experimental/expectations/expect_column_sum_to_be.py b/contrib/experimental/great_expectations_experimental/expectations/expect_column_sum_to_be.py
new file mode 100644
--- /dev/null
+++ b/contrib/experimental/great_expectations_experimental/expectations/expect_column_sum_to_be.py
@@ -0,0 +1,119 @@
+"""
+This is a template for creating custom ColumnExpectations.
+For detailed instructions on how to use it, please see:
+    https://docs.greatexpectations.io/docs/guides/expectations/creating_custom_expectations/how_to_create_custom_column_aggregate_expectations
+"""
+
+from typing import Dict, Optional
+
+from great_expectations.core.expectation_configuration import ExpectationConfiguration
+from great_expectations.execution_engine import ExecutionEngine
+from great_expectations.expectations.expectation import ColumnExpectation
+
+
+# This class defines the Expectation itself
+class ExpectColumnSumToBe(ColumnExpectation):
+    """Expect the sum of a column to be exactly a value."""
+
+    # These examples will be shown in the public gallery.
+    # They will also be executed as unit tests for your Expectation.
+    examples = [
+        {
+            "data": {"a": [1, 2, 3, 4, 5]},
+            "tests": [
+                {
+                    "title": "basic_positive_test",
+                    "exact_match_out": False,
+                    "include_in_gallery": True,
+                    "in": {"column": "a", "sum_total": 15},
+                    "out": {"success": True},
+                },
+                {
+                    "title": "basic_negative_test",
+                    "exact_match_out": False,
+                    "include_in_gallery": True,
+                    "in": {"column": "a", "sum_total": 14},
+                    "out": {"success": False},
+                },
+            ],
+            "test_backends": [
+                {
+                    "backend": "pandas",
+                    "dialects": None,
+                },
+                {
+                    "backend": "sqlalchemy",
+                    "dialects": ["sqlite", "postgresql"],
+                },
+                {
+                    "backend": "spark",
+                    "dialects": None,
+                },
+            ],
+        }
+    ]
+
+    # This is a tuple consisting of all Metrics necessary to evaluate the Expectation.
+    metric_dependencies = ("column.sum",)
+
+    # This a tuple of parameter names that can affect whether the Expectation evaluates to True or False.
+    success_keys = ("sum_total",)
+
+    # This dictionary contains default values for any parameters that should have default values.
+    default_kwarg_values = {}
+
+    def validate_configuration(self, configuration: Optional[ExpectationConfiguration]):
+        """
+        Validates that a configuration has been set, and sets a configuration if it has yet to be set. Ensures that
+        necessary configuration arguments have been provided for the validation of the expectation.
+
+        Args:
+            configuration (OPTIONAL[ExpectationConfiguration]): \
+                An optional Expectation Configuration entry that will be used to configure the expectation
+        Returns:
+            True if the configuration has been validated successfully. Otherwise, raises an exception
+        """
+
+        super().validate_configuration(configuration)
+        if configuration is None:
+            configuration = self.configuration
+
+        # # Check other things in configuration.kwargs and raise Exceptions if needed
+        # try:
+        #     assert (
+        #         ...
+        #     ), "message"
+        #     assert (
+        #         ...
+        #     ), "message"
+        # except AssertionError as e:
+        #     raise InvalidExpectationConfigurationError(str(e))
+
+        return True
+
+    # This method performs a validation of your metrics against your success keys, returning a dict indicating the success or failure of the Expectation.
+    def _validate(
+        self,
+        configuration: ExpectationConfiguration,
+        metrics: Dict,
+        runtime_configuration: dict = None,
+        execution_engine: ExecutionEngine = None,
+    ):
+        actual_value = metrics["column.sum"]
+        predicted_value = self.get_success_kwargs(configuration).get("sum_total")
+        success = actual_value == predicted_value
+        return {"success": success, "result": {"observed_value": actual_value}}
+
+    # This object contains metadata for display in the public Gallery
+    library_metadata = {
+        "tags": [
+            "column aggregate expectation",
+        ],  # Tags for this Expectation in the Gallery
+        "contributors": [  # Github handles for all contributors to this Expectation.
+            "@joshua-stauffer",  # Don't forget to add your github handle here!
+        ],
+    }
+
+
+if __name__ == "__main__":
+    ExpectColumnSumToBe().print_diagnostic_checklist()


Test patch: