how to create a new uml file and use the name of the loaded json file in python?

I have this code where i am loading JSON files

json_files = glob.glob('JSON/*.json', recursive=True)

Name of json files are as follows:

abc.json
xyz.json

Now i have this function where i am creating a Gantt chart using the JSON files:

def creategantt():
   for single_file in uml_files:
     with open(Need help here, "w") as f: 
       # Note: uncomment both 2 lines below if want to start the project XX weeks from today 
       ago.
       # today = datetime.datetime.now().date()
       # start_project_date = today + datetime.timedelta(weeks = -8)
       f.write("@startuml\nprintscale weekly\nProject starts 2022-08-01\n")
       # Extract information for Gantt chart
       for stuff in json_data["releases"]:
           new_line = "[Release " + stuff["release"] + "] starts " + stuff["start_date"] + " 
           and 
           ends " + stuff["end_date"] + "\n"
           f.write(new_line)
           print(new_line)
       f.write("@enduml")

As I have multiple json file what i am trying is to open each json file one by one and create Gannt chart. The gant chart should be saved in a new file as abc.uml and 2nd time when the code runs the new file should be created as xyz.uml. Can someone guide me here how can i create a file using the same name as JSON file name?