You can create a new column for the difference
> df['C'] = df['B'].diff()
> print df
# A B C
0 1 2 3 NaN
1 2 3 3 0
2 3 4 4 1
3 4 5 4 0
4 5 5 4 0
> df_filtered = df[df['C'] != 0]
> print df_filtered
# A B C
2 3 4 4 1
This will your required rows