# import necessary libraries
import pandas as pd

# create sample series
fruits = pd.Series(['apple', 'banana', 'mango', 'apple',
                      'mango', 'apple', 'apple', 'banana'])
values = pd.Series([1, 2, 3, 4, 5, 6, 7, 8])

# create a dataframe
df = pd.DataFrame({'fruits': fruits, 'values': values})

# calculate mean of grouped values using list comprehension
grouped_mean = {group: df.loc[df['fruits'] == group, 'values'].mean() 
                for group in df['fruits'].unique()}

# print the results
print(grouped_mean)