I want writing function for sorted_average() .  I calculated average of data in input file and write them in my output file. then i want sort data of out put file. but my cod not working...

my out put file is : 

• mandana,7.5
• hamid,6.066666666666666
• sina,11.285714285714286
• sara,9.75
• soheila,7.833333333333333
• ali,5.0
• sarvin,11.375

I want sorting this numbers....can help me?

def calculate_sorted_averages(input_file_name, output_file_name):
    labels = ['name', 'mean_grade']

    with open(input_file_name, 'r') as file_obj:
        csv_obj = csv.reader(file_obj)
       

        data = [
            [row[0], statistics.mean(float(grade) for grade in row[1:])]
            for row in csv_obj]


        # sort data according to `name`
    sorted(data, key=lambda x: x[0])

    with open(output_file_name, 'w') as file_obj:
            obj = csv.writer(file_obj)
            csv_obj.writerow(labels)
            for row in data:
                csv_obj.writerow(row)
    return file_obj

calculate_sorted_averages('input.csv','output.csv')