Python extract a week number from the specific date

Question

I would like to extract a week number from a data in panda dataframe but starting from the SPECIFIC date.

For example from 4th April:

20/04/2010 --> 1

27/04/2010 --> 2

04/05/2010 --> 3

and so on..

Any idea?

Thank you in advance!

you can try getting the day count from the beginning of that year and divide it by 7. I'm not sure whether it will always give the right number. — atakanyenel, Mar 05 '17 at 21:52
Does the week begin at the specified date or at the first day of the week of the specified date? — Eric Duminil, Mar 05 '17 at 22:45

score 2 · Accepted Answer · answered Mar 05 '17 at 22:43

2

Just calculate the difference in days between 2 dates, divide by 7 and add 1 :

from datetime import date

origin = date(2010, 4, 20)

def week_number_from(my_date, origin):
    return (my_date - origin).days / 7 + 1

answered Mar 05 '17 at 22:43

Eric Duminil

@Giada if this answers your question, consider upvoting the answer and selecting it as your chosen answer by clicking the green check. – piRSquared Mar 07 '17 at 07:19

jeffery_the_wind · Answer 2 · 2017-03-08T16:16:04.977

1

Use pandas to_datetime to parse your date column if it is not already in datetime format.

Then use the date time method weekday.

my_dataframe['week_nums'] = pandas.to_datetime(my_dataframe['date_col']).weekday()

Sorry I saw you want week day from specific date, will update answer... it is easy to calculate the difference between 2 dates.

edited Mar 08 '17 at 16:16

answered Mar 05 '17 at 21:53

jeffery_the_wind

Thanks! But this shows a week number starting from the 1st January.. :/ – Sheron Mar 05 '17 at 21:59

2 Answers2