[Python] Support encode for array of string in serialization and deserialization

.chronus/changes/python-array-encode-2025-11-5-10-12-9.md

@@ -0,0 +1,7 @@
+---
+changeKind: feature
+packages:
+  - "@typespec/http-client-python"
+---
+
+Support encode for array of string in serialization and deserialization

packages/http-client-python/emitter/src/types.ts

@@ -246,6 +246,7 @@ function emitProperty(
     flatten: property.flatten,
     isMultipartFileInput: isMultipartFileInput,
     xmlMetadata: getXmlMetadata(property),
+    encode: property.encode,
   };
 }
 

packages/http-client-python/generator/pygen/codegen/models/property.py

@@ -40,6 +40,7 @@ def __init__(
         self.is_multipart_file_input: bool = yaml_data.get("isMultipartFileInput", False)
         self.flatten = self.yaml_data.get("flatten", False) and not getattr(self.type, "flattened_property", False)
         self.original_tsp_name: Optional[str] = self.yaml_data.get("originalTspName")
+        self.encode: Optional[str] = self.yaml_data.get("encode")
 
     def pylint_disable(self) -> str:
         retval: str = ""

packages/http-client-python/generator/pygen/codegen/serializers/model_serializer.py

@@ -329,6 +329,8 @@ def declare_property(self, prop: Property) -> str:
             args.append("is_multipart_file_input=True")
         elif hasattr(prop.type, "encode") and prop.type.encode:  # type: ignore
             args.append(f'format="{prop.type.encode}"')  # type: ignore
+        elif prop.encode:
+            args.append(f'format="{prop.encode}"')
 
         if prop.xml_metadata:
             args.append(f"xml={prop.xml_metadata}")

packages/http-client-python/generator/pygen/codegen/templates/model_base.py.jinja2

@@ -179,6 +179,17 @@ _VALID_RFC7231 = re.compile(
     r"(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)\s\d{4}\s\d{2}:\d{2}:\d{2}\sGMT"
 )
 
+_ARRAY_ENCODE_MAPPING = {
+    "pipeDelimited": "|",
+    "spaceDelimited": " ",
+    "commaDelimited": ",",
+    "newlineDelimited": "\n",
+}
+
+def _deserialize_array_encoded(delimit: str, attr):
+    if isinstance(attr, str):
+        return attr.split(delimit)
+    return attr
 
 def _deserialize_datetime(attr: typing.Union[str, datetime]) -> datetime:
     """Deserialize ISO-8601 formatted string into Datetime object.
@@ -323,6 +334,8 @@ _DESERIALIZE_MAPPING_WITHFORMAT = {
 def get_deserializer(annotation: typing.Any, rf: typing.Optional["_RestField"] = None):
     if annotation is int and rf and rf._format == "str":
         return _deserialize_int_as_str
+    if annotation is list and rf and rf._format in _ARRAY_ENCODE_MAPPING:
+        return functools.partial(_deserialize_array_encoded, _ARRAY_ENCODE_MAPPING[rf._format])
     if rf and rf._format:
         return _DESERIALIZE_MAPPING_WITHFORMAT.get(rf._format)
     {% if code_model.has_external_type %}
@@ -497,6 +510,8 @@ def _is_model(obj: typing.Any) -> bool:
 
 def _serialize(o, format: typing.Optional[str] = None):  # pylint: disable=too-many-return-statements
     if isinstance(o, list):
+        if format in _ARRAY_ENCODE_MAPPING and all(isinstance(x, str) for x in o):
+            return _ARRAY_ENCODE_MAPPING[format].join(o)
         return [_serialize(x, format) for x in o]
     if isinstance(o, dict):
         return {k: _serialize(v, format) for k, v in o.items()}