How do I get the day of week given a date?

Question

I want to find out the following: given a date (datetime object), what is the corresponding day of the week?

For instance, Sunday is the first day, Mond

Answer 1

If you want to generate a column with a range of dates (Date) and generate a column that goes to the first one and assigns the Week Day (Week Day), do the following (I will used the dates ranging from 2008-01-01 to 2020-02-01):

import pandas as pd
dr = pd.date_range(start='2008-01-01', end='2020-02-1')
df = pd.DataFrame()
df['Date'] = dr
df['Week Day'] = pd.to_datetime(dr).weekday

The output is the following:

The Week Day varies from 0 to 6, where 0 corresponds to Monday and 6 to Sunday.

Answer 2

Assuming you are given the day, month, and year, you could do:

import datetime
DayL = ['Mon','Tues','Wednes','Thurs','Fri','Satur','Sun']
date = DayL[datetime.date(year,month,day).weekday()] + 'day'
#Set day, month, year to your value
#Now, date is set as an actual day, not a number from 0 to 6.

print(date)

Answer 3

We can take help of Pandas:

import pandas as pd

As mentioned above in the problem We have:

datetime(2017, 10, 20)

If execute this line in the jupyter notebook we have an output like this:

datetime.datetime(2017, 10, 20, 0, 0)

Using weekday() and weekday_name:

If you want weekdays in integer number format then use:

pd.to_datetime(datetime(2017, 10, 20)).weekday()

The output will be:

4

And if you want it as name of the day like Sunday, Monday, Friday, etc you can use:

pd.to_datetime(datetime(2017, 10, 20)).weekday_name

The output will be:

'Friday'

If having a dates column in Pandas dataframe then:

Now suppose if you have a pandas dataframe having a date column like this: pdExampleDataFrame['Dates'].head(5)

0   2010-04-01
1   2010-04-02
2   2010-04-03
3   2010-04-04
4   2010-04-05
Name: Dates, dtype: datetime64[ns]

Now If we want to know the name of the weekday like Monday, Tuesday, ..etc we can use .weekday_name as follows:

pdExampleDataFrame.head(5)['Dates'].dt.weekday_name

the output will be:

0    Thursday
1      Friday
2    Saturday
3      Sunday
4      Monday
Name: Dates, dtype: object

And if we want the integer number of weekday from this Dates column then we can use:

pdExampleDataFrame.head(5)['Dates'].apply(lambda x: x.weekday())

The output will look like this:

0    3
1    4
2    5
3    6
4    0
Name: Dates, dtype: int64

Answer 4

If you'd like to have the date in English:

>>> from datetime import datetime
>>> datetime.today().strftime('%A')
'Wednesday'

Read more: https://docs.python.org/2/library/datetime.html#strftime-strptime-behavior

Answer 5

import numpy as np

def date(df):

df['weekday'] = df['date'].dt.day_name()

conditions = [(df['weekday'] == 'Sunday'),
          (df['weekday'] == 'Monday'),
          (df['weekday'] == 'Tuesday'),
          (df['weekday'] == 'Wednesday'),
          (df['weekday'] == 'Thursday'),
          (df['weekday'] == 'Friday'),
          (df['weekday'] == 'Saturday')]

choices = [0, 1, 2, 3, 4, 5, 6]

df['week'] = np.select(conditions, choices)

return df

Answer 6

I solved this for a CodeChef question.

import datetime
dt = '21/03/2012'
day, month, year = (int(x) for x in dt.split('/'))    
ans = datetime.date(year, month, day)
print (ans.strftime("%A"))