Week number of the month

Question

Does pandas (python) offer a way to easily get the current week of the month (1:4) from a date series?

data = {'date': ['2014-05-01', '2014-05-01', '2014-05-02', '2014-05-02', '2014-05-02', '2014-05-02', '2014-05-03', '2014-05-03', '2014-05-04', '2014-05-04']}
df = pd.DataFrame(data, columns = ['date'])
df['date']=pd.to_datetime(df['date'])

def week_of_month(dt):
    """ Returns the week of the month for the specified date.
    """
    first_day = dt.replace(day=1)
    dom = dt.day
    adjusted_dom = dom + first_day.weekday()
    return int(ceil(adjusted_dom/7.0))


df ['week']=np.nan
for i in range(len(df)):
    df ['week'][i] =  week_of_month(df.date.iloc[i])

with a short data set it works but with a large data set takes to much resources

Yes, that's what I meant.[link] (https://stackoverflow.com/questions/3806473/python-week-number-of-the-month) in this post there is the answer but just for a specific date. — Pablo Yépez Daza, Dec 27 '17 at 04:01
some locales start the week with sunday, others with monday. — ShpielMeister, Dec 27 '17 at 04:06

score 2 · Answer 1 · answered Dec 27 '17 at 05:21

Problem solved:

data = {'date_x': ['2014-05-01', '2014-05-01', '2014-05-02', '2014-05-02', '2014-05-02', '2014-05-02', '2014-05-03', '2014-05-03', '2014-05-04', '2014-05-04']}
df = pd.DataFrame(data, columns = ['date_x'])
df['date']=pd.to_datetime(df['date_x'])

df['first_day_aux']=pd.to_datetime(df['date_x'][0][:8]+'01') 
df['day']=df['date'].dt.day 
df['adjusted_dom']=df['day']+df['first_day_aux'].dt.dayofweek
df['week']=np.int_(np.ceil(df['adjusted_dom']/7.0))

Week number of the month

1 Answers1

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