Merge pull request #93 from digital-asset/python-decimal-formatting

python: Support formatting decimals that are very small.

Author: da-tanabe

VERSION

@@ -1 +1 @@
-6.8.1
+6.8.2

python/dazl/protocols/v1/pb_ser_command.py

@@ -10,14 +10,13 @@
 from ... import LOG
 # noinspection PyPep8Naming
 from . import model as G
-from ...damlast.daml_lf_1 import TypeConName
 from ...model.core import ContractId
 from ...model.types import VariantType, RecordType, ListType, ContractIdType, \
     UnsupportedType, TemplateChoice, TypeReference, TypeEvaluationContext, SCALAR_TYPE_UNIT, \
     TextMapType, OptionalType, EnumType
 from ...model.writing import AbstractSerializer, CommandPayload
 from ...util.prim_types import to_boolean, to_date, to_datetime, to_decimal, to_int, to_str, \
-    decode_variant_dict
+    to_ledger_api_decimal, decode_variant_dict
 
 # noinspection PyPackageRequirements
 from google.protobuf.empty_pb2 import Empty
@@ -154,7 +153,7 @@ def serialize_int(self, context: TypeEvaluationContext, obj: Any) -> R:
         return 'int64', to_int(obj)
 
     def serialize_decimal(self, context: TypeEvaluationContext, obj: Any) -> R:
-        return 'numeric', str(to_decimal(obj))
+        return 'numeric', to_ledger_api_decimal(to_decimal(obj))
 
     def serialize_party(self, context: TypeEvaluationContext, obj: Any) -> R:
         return 'party', to_str(obj)

python/dazl/util/prim_types.py

@@ -46,6 +46,11 @@ def to_boolean(obj) -> bool:
     raise ValueError(f'Could not parse as a boolean: {obj!r}')
 
 
+def to_ledger_api_decimal(obj: 'Decimal') -> str:
+    precision = max(0, -obj.as_tuple().exponent)
+    return format(obj, f'.{precision}f')
+
+
 @overload
 def to_timedelta(obj: TimeDeltaConvertible) -> timedelta: ...
 

python/pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "dazl"
-version = "6.8.1"
+version = "6.8.2"
 description = "high-level Ledger API client for DAML ledgers"
 license = "Apache-2.0"
 authors = ["Davin K. Tanabe <davin.tanabe@digitalasset.com>"]

python/tests/unit/test_decimal_serialize.py

@@ -0,0 +1,36 @@
+from decimal import Decimal
+
+from dazl.util.prim_types import to_ledger_api_decimal
+
+
+def test_one():
+    assert to_ledger_api_decimal(Decimal("1")) == "1"
+
+
+def test_ten():
+    assert to_ledger_api_decimal(Decimal("10")) == "10"
+
+
+def test_one_tenth():
+    assert to_ledger_api_decimal(Decimal("0.1")) == "0.1"
+
+
+def test_one_trillionth():
+    assert to_ledger_api_decimal(Decimal("0.000000000001")) == "0.000000000001"
+
+
+def test_one_trillion():
+    assert to_ledger_api_decimal(Decimal("1000000000000")) == "1000000000000"
+
+
+def test_one_trillionth_and_a_bit():
+    assert to_ledger_api_decimal(Decimal("0.0000000000011")) == "0.0000000000011"
+
+
+def test_quarter_quadrillion():
+    assert to_ledger_api_decimal(Decimal("250000000000000")) == "250000000000000"
+
+
+def test_quarter_quadrillion_and_a_bit():
+    assert to_ledger_api_decimal(Decimal("250000000000000.0000000000011")) == "250000000000000.0000000000011"
+