feat: Add round post processor

README.md

@@ -21,7 +21,7 @@ schema = {
         {"key": "vat", "column-number": 10, "type": "decimal", "optional": False},
         {"key": "initial-price", "column-number": 11, "type": "decimal", "post-processors": {"name": "divide", "parameters": {"denominator": 100}}},
         {"key": "unit-of-measurement", "column-number": 12, "type": "int", "pre-processors": [{"name": "map", "parameters": {"values": {"K": 0, "A": 1, "L": 2}}}]},
-        {"key": "volume", "column-number": 13, "type": "decimal"},
+        {"key": "volume", "column-number": 13, "type": "decimal", "post-processors": {"name": "round", "parameters": {"precision": 3}}},
     ]
 }
 
@@ -121,3 +121,4 @@ assert rows == [{"name": "Joe"}, {"name": "William"}, {"name": "Jack"}, {"name":
 #### Post-processors
 
 - divide
+- round

magicparse/post_processors.py

@@ -42,4 +42,24 @@ def key() -> str:
         return "divide"
 
 
-builtins = [Divide]
+class Round(PostProcessor):
+    Number = TypeVar("Number", int, float, Decimal)
+
+    def __init__(self, precision: int) -> None:
+        if precision < 0:
+            raise ValueError(
+                "post-processor 'round': "
+                "'precision' parameter must be a positive or zero integer"
+            )
+
+        self.precision = precision
+
+    def apply(self, value: Number) -> Number:
+        return round(value, self.precision)
+
+    @staticmethod
+    def key() -> str:
+        return "round"
+
+
+builtins = [Divide, Round]

tests/test_post_processors.py

@@ -49,6 +49,22 @@ def test_divide_decimal(self):
         assert post_processor.apply(Decimal("1.63")) == Decimal("0.0163")
 
 
+class TestRound(TestCase):
+    def test_with_negative_precision(self):
+        error_message = (
+            "post-processor 'round': "
+            "'precision' parameter must be a positive or zero integer"
+        )
+        with pytest.raises(ValueError, match=error_message):
+            PostProcessor.build({"name": "round", "parameters": {"precision": -2}})
+
+    def test_with_valid_precision(self):
+        post_processor = PostProcessor.build(
+            {"name": "round", "parameters": {"precision": 2}}
+        )
+        assert post_processor.apply(3.14159265359) == 3.14
+
+
 class TestRegister(TestCase):
     class NoThanksPostProcessor(PostProcessor):
         @staticmethod