Fix coin selection

Author: nielstron

pycardano/certificate.py

@@ -5,7 +5,11 @@
 
 from pycardano.exception import DeserializeException
 from pycardano.hash import PoolKeyHash, ScriptHash, VerificationKeyHash
-from pycardano.serialization import ArrayCBORSerializable, limit_primitive_type, ArrayBase
+from pycardano.serialization import (
+    ArrayCBORSerializable,
+    limit_primitive_type,
+    ArrayBase,
+)
 
 __all__ = [
     "Certificate",

pycardano/coinselection.py

@@ -186,22 +186,18 @@ def _split_by_asset(value: Value) -> List[Value]:
         assets = [Value(value.coin)]
 
         # Extract native assets
-        for policy_id in value.multi_asset:
-            for asset_name in value.multi_asset[policy_id]:
-                assets.append(
-                    Value.from_primitive(
-                        [
-                            0,
-                            {
-                                policy_id.payload: {
-                                    asset_name.payload: value.multi_asset[policy_id][
-                                        asset_name
-                                    ]
-                                }
-                            },
-                        ]
-                    )
+        for policy_id, policy_id_dict in value.multi_asset.items():
+            for asset_name, amount in policy_id_dict.items():
+                if not amount:
+                    # skip 0 amounts
+                    continue
+                value = Value.from_primitive(
+                    [
+                        0,
+                        {policy_id.payload: {asset_name.payload: amount}},
+                    ]
                 )
+                assets.append(value)
 
         return assets