How to create a datetime column from year, month and day columns in pandas ?

Examples of how to create a datetime column from year, month and day columns in pandas:

Table of contents

Create a dataframe
Create a datetime column
Set datetime column as the dataframe index
References

Create a dataframe

Let's first create a dataframe in pandas with 3 columns "Year", "Month" and "Day":

import pandas as pd
import random
import itertools

year_list = []
month_list = []
day_list = []

for combination in itertools.product([2015], [1,2,3,4], [5,15,25]):
        #print(combination) 
        year_list.append( combination[0] )
        month_list.append( combination[1] )
        day_list.append( combination[2] )

data = {'Year':year_list,
                'Month':month_list,
                'Day':day_list,
                'Random Integer':[random.randrange(1, 10) for i in range(len(year_list))]}

df = pd.DataFrame(data=data)

print(df)

returns for example

            Year  Month  Day  Random Integer
0   2015      1    5               7
1   2015      1   15               5
2   2015      1   25               6
3   2015      2    5               4
4   2015      2   15               1
5   2015      2   25               2
6   2015      3    5               4
7   2015      3   15               9
8   2015      3   25               3
9   2015      4    5               1
10  2015      4   15               3
11  2015      4   25               7

Create a datetime column

To create a new datetime column using 'Year', 'Month' and 'Day' columns, a solution is to use to_datetime():

df['Datetime'] = pd.to_datetime( df[['Year', 'Month', 'Day']])

returns

        Year  Month  Day  Random Integer   Datetime
0   2015      1    5               7 2015-01-05
1   2015      1   15               5 2015-01-15
2   2015      1   25               6 2015-01-25
3   2015      2    5               4 2015-02-05
4   2015      2   15               1 2015-02-15
5   2015      2   25               2 2015-02-25
6   2015      3    5               4 2015-03-05
7   2015      3   15               9 2015-03-15
8   2015      3   25               3 2015-03-25
9   2015      4    5               1 2015-04-05
10  2015      4   15               3 2015-04-15
11  2015      4   25               7 2015-04-25

Set datetime column as the dataframe index

Now, if you want to set the datetime column as the dataframe index,a solution is to use set_index():

df.set_index('Datetime', inplace=True)

returns

                     Year  Month  Day  Random Integer
Datetime                                    
2015-01-05  2015      1    5               7
2015-01-15  2015      1   15               5
2015-01-25  2015      1   25               6
2015-02-05  2015      2    5               4
2015-02-15  2015      2   15               1
2015-02-25  2015      2   25               2
2015-03-05  2015      3    5               4
2015-03-15  2015      3   15               9
2015-03-25  2015      3   25               3
2015-04-05  2015      4    5               1
2015-04-15  2015      4   15               3
2015-04-25  2015      4   25               7

Can be used to plot a time series:

How to create a datetime column from year, month and day columns in pandas ?

Note to reset the index:

df.reset_index(inplace=True)

References

Hi, I'm Ben, the Founder of moonbooks.org. I work as a research scientist specializing in Earth satellite remote sensing, particularly focusing on Fire detection using VIIRS and ABI sensors. My areas of expertise include Python, Machine Learning, and Open Science. Feel free to reach out if you notice any errors on the site. I am constantly striving to enhance it. Thank you!

How to create a datetime column from year, month and day columns in pandas ?

Create a dataframe

Create a datetime column

Set datetime column as the dataframe index

References

Benjamin

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