Hi Li., and all,
- What are your goals?
You can not directly mix component and class....
If you want to mix `component diagram` with `class diagram`, for that use dummy label and sub-diagram like:
@startuml
package "Web Server Application" {
[Web Server]
[Database]
[Client Browser]
[Load Balancer]
[Web Server] --> [Database] : Read/Write Data
[Web Server] --> [Client Browser] : Serve Web Pages
[Client Browser] --> [Web Server] : Send HTTP Requests
[Client Browser] --> [Load Balancer] : Send HTTP Requests
[Load Balancer] --> [Web Server] : Distribute Requests
}
package "Python Code" {
[Web Server] --> [Python Code] : Handle HTTP Requests
[Python Code] --> [Database] : Query Database
[Python Code] --> [Client Browser] : Send HTTP Responses
label l [{{
class "PythonCode" {
+handle_request(request: HttpRequest) : HttpResponse
}
class HttpRequest {
+method : str
+path : str
+headers : dict
+body : str
}
class HttpResponse {
+status_code : int
+headers : dict
+body : str
}
class Database {
+query(sql: str) : Result
}
class Result {
+rows : list
}
}}]
}
@enduml

Regards.
Th.