Create a day-of-week column in a Pandas dataframe using Python

Question

Create a day-of-week column in a Pandas dataframe using Python

I’d like to read a csv file into a pandas dataframe, parse a column of dates from string format to a date object, and then generate a new column that indicates the day of the week.

This is what I’m trying:

What I’d like to do is something like:

import pandas as pd  import csv  df = pd.read_csv('data.csv', parse_dates=['date']))  df['day-of-week'] = df['date'].weekday()   AttributeError: 'Series' object has no attribute 'weekday' 

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Thank you for your help. James

Answer 1

Pandas 0.23+

Use pandas.Series.dt.day_name(), since pandas.Timestamp.weekday_name has been deprecated:

import pandas as pd   df = pd.DataFrame({'my_dates':['2015-01-01','2015-01-02','2015-01-03'],'myvals':[1,2,3]}) df['my_dates'] = pd.to_datetime(df['my_dates'])  df['day_of_week'] = df['my_dates'].dt.day_name() 

Output:

    my_dates  myvals day_of_week 0 2015-01-01       1    Thursday 1 2015-01-02       2      Friday 2 2015-01-03       3    Saturday 

Pandas 0.18.1+

As user jezrael points out below, dt.weekday_name was added in version 0.18.1 Pandas Docs

import pandas as pd  df = pd.DataFrame({'my_dates':['2015-01-01','2015-01-02','2015-01-03'],'myvals':[1,2,3]}) df['my_dates'] = pd.to_datetime(df['my_dates']) df['day_of_week'] = df['my_dates'].dt.weekday_name 

Output:

    my_dates  myvals day_of_week 0 2015-01-01       1    Thursday 1 2015-01-02       2      Friday 2 2015-01-03       3    Saturday 

Original Answer:

Use this:

http://pandas.pydata.org/pandas-docs/stable/generated/pandas.Series.dt.dayofweek.html

See this:

Get weekday/day-of-week for Datetime column of DataFrame

If you want a string instead of an integer do something like this:

import pandas as pd  df = pd.DataFrame({'my_dates':['2015-01-01','2015-01-02','2015-01-03'],'myvals':[1,2,3]}) df['my_dates'] = pd.to_datetime(df['my_dates']) df['day_of_week'] = df['my_dates'].dt.dayofweek  days = {0:'Mon',1:'Tues',2:'Weds',3:'Thurs',4:'Fri',5:'Sat',6:'Sun'}  df['day_of_week'] = df['day_of_week'].apply(lambda x: days[x]) 

Output:

    my_dates  myvals day_of_week 0 2015-01-01       1       Thurs 1 2015-01-02       2         Fri 2 2015-01-01       3       Thurs