# import necessary libraries
import pandas as pd

# define your series
ser1 = pd.Series([1, 2, 3, 4, 5])
ser2 = pd.Series([4, 5, 6, 7, 8])

# use isin() method
mask = ser1.isin(ser2)

# filter series1 using ~mask
result = ser1[~mask]

# print result 
print(*result, sep = '\n')