["python","pandas","datetime"]
converting a pandas date to week number

I would like to extract a week number from data in a pandas dataframe. The date format is datetime64[ns] I have normalized the date to remove the time from it df['Date'] = df['Date'].apply(pd.datetools.normalize_date) so the date now looks like - 2015-06-17 in the data frame column and now I like to convert that to a week number.
Just access the week attribute of Series.dt.isocalendar(): Example: In [286]: df['Date'].dt.isocalendar().week Out[286]: 0 25 dtype: int64 In [287]: df['Week_Number'] = df['Date'].dt.isocalendar().week df Out[287]: Date Week_Number 0 2015-06-17 25