How to Retrieve the Year from a DateTime Object

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Problem Formulation and Solution Overview

This article will show you how to retrieve a year from a DateTime Object in Python. Whether that being a year from a DateTime Object, a DataFrame, or even a NumPy array.


πŸ’¬ Question: How would we write code to retrieve the Year from a DateTime Object?

We can accomplish this task by one of the following options:


Method 1: Use today().year()

This method uses the today() function to retrieve the current date and year() to extract the current year from that date.

import datetime

cur_year = datetime.date.today().year
print(cur_year)

The first line in the above code snippet imports Python’s built-in datetime library. This library allows access to and manipulation of dates and times in Python.

The following line first calls datetime (cur_year = datetime). This returns a DateTime class module similar to below:

<module 'datetime' from 'C:\python\lib\datetime.py'

Next, date is appended to datetime (cur_year = datetime.date) and returns a datetime.date class similar to below:

<class 'datetime.date'>

Then, today() is appended (cur_year = datetime.date.today()) and retrieves the current date.

2022-10-27

Finally, year() is appended to retrieve the current year from the current date shown above. The result is output to the terminal.

2022
Working with date-time in Pandas

Method 2: Use now() and year()

This method uses the now() function to retrieve the current date and time and year to retrieve the current year from that date.

import datetime

cur_year = datetime.datetime.now().year
print(cur_year)

The first line in the above code snippet imports Python’s built-in datetime library. This library allows access to and manipulation of dates and times in Python.

The following line first calls datetime (cur_year = datetime). This returns a datetime class module similar to below:

<module 'datetime' from 'C:\python\lib\datetime.py'>

Next, datetime is appended to datetime (cur_year = datetime.datetime) and returns a datetime.date class similar to below:

<class 'datetime.date'>

Then, now() is appended (cur_year = datetime.date.now()) and retrieves the current date and time.

2022-10-27 12:27:15.062809

Finally, year is appended to retrieve the current year from the current date and time shown above. The result is output to the terminal.

2022

Method 3: Use DatetimeIndex()

This method uses Panda’s DatetimeIndex() function to retrieve the year from each Date column in a DataFrame.

Before running this code snippet, the Pandas library needs to be installed. Click here for installation instructions.

import pandas as pd

df = pd.read_csv('staff.csv', usecols=['EMPLOYEE_ID', 'HIRE_DATE'])
df['HIRE_YR'] = pd.DatetimeIndex(df['HIRE_DATE']).year
print(df['HIRE_YR'])

The first line in the above code snippet imports the Pandas library. This library allows access to and manipulation of DataFrames.

The following line reads in two (2) columns and five (5) rows from the CSV file staff.csv. The results save to the DataFrame, df.

EMPLOYEE_IDHIRE_DATE
019821-JUN-07
219913-JAN-08
320017-SEP-03
420117-FEB-04
520217-AUG-05

The following line retrieves the year from each record in the DataFrame and saves the results to a new column, by using DatetimeIndex() and passing it df['HIRE_DATE'] as an argument. The results save to a new column df['HIRE_YR'].

The results are output to the terminal.

02007
12008
22003
32004
42005
Name: HIRE_YR, dtype: int64
10 Minutes to Pandas in 5 Minutes (Okay 8)

Method 4: Use Timestamp()

This method uses the Panda’s Timestamp() function to retrieve the year from a Date column in a DataFrame.

Before running this code snippet, the Pandas library needs to be installed. Click here for installation instructions.

import pandas as pd
  
the_date = pd.Timestamp(year=2022, month=12, day=25, hour=1, second=1, tz='US/Pacific')
print(the_date.year)

The first line in the above code snippet imports the Pandas library. This library allows access to and manipulation of DataFrames.

The following line calls the timestamp() function and passes it the following arguments:

  • A year
  • A month
  • A Day
  • An Hour
  • A Second
  • A TimeZone

The results save to the_date. If output to the terminal, the following would display:

2022-12-25 01:00:01-08:00

Finally, the year is retrieved and output to the terminal.

2022

Method 5: Use strptime() and a lambda

This method uses the datetime and strptime() function in conjunction with a lambda to retrieve the year from a Date column in a DataFrame.

Before running this code snippet, the Pandas library needs to be installed. Click here for installation instructions.

import datetime
import pandas as pd 

df = pd.read_csv('staff.csv', usecols=['EMPLOYEE_ID', 'HIRE_DATE']).head()
df.loc[:,'HIRE_YEAR'] = df.loc[:,'HIRE_DATE'].map(lambda x: datetime.datetime.strptime(str(x),'%d-%b-%y').year)
print(df)

The first two (2) lines of the above snippet import the datetime library and the Pandas library. These two (2) libraries allow access to and manipulation of datetimes as well as DataFrames.

The following line reads in two (2) columns and five (5) rows from the CSV file staff.csv. The results save to the DataFrame, df.

EMPLOYEE_IDHIRE_DATE
019821-JUN-07
219913-JAN-08
320017-SEP-03
420117-FEB-04
520217-AUG-05

The following line uses loc, map(), a lambda, strptime(), and year to retrieve the year from each row in the df['HIRE_DATE'] column of the DataFrame. The results save as a new column, df['HIRE_YEAR'], in the DataFrame.

EMPLOYEE_IDHIRE_DATEHIRE_YEAR
019821-JUN-072007
219913-JAN-082008
320017-SEP-032003
420117-FEB-042004
520217-AUG-052005
Converting String into Datetime

Method 6: Use to_datetime()

Thie method uses the NumPy and Pandas library in conunction with to_datetime() to retrieve the year.

Before running this code snippet, the NumPy and Pandas libraries must be installed.

  • Click here to install the NumPy library.
  • Click here to install the Pandas library.
import numpy as np 
import pandas as pd 

dates = np.array(['2010-10-17', '2011-05-13', '2012-01-15'], dtype=np.datetime64)
print(pd.to_datetime(dates).year)

The first two lines of the above code snippet import the NumPy and the Pandas library.

The following line is passed a NumPy array containing three (3) dates. These dates are set to the type of datetime64. The results save to dates. If output to the terminal, the following would display”

['2010-10-17' '2011-05-13' '2012-01-15']

Finally, the year is retrieved from the above and output to the terminal.

Int64Index([2010, 2011, 2012], dtype='int64')
NumPy Tutorial - Everything You Need to Know to Get Started

Bonus:

If you have a list of dates and the location of the year falls in the same place, slicing works!

dates = ['2021-01-15', '2022-08-01', '2023-09-01', '2224-12-01']
results = [d[:4] for d in dates]
print(results)

Results

['2021', '2022', '2023', '2224']

Summary

This article has provided 7 ways to retrieve a year from a DateTime object to select the best fit for your coding requirements.

Good Luck & Happy Coding!


Programming Humor – Python

“I wrote 20 short programs in Python yesterday. It was wonderful. Perl, I’m leaving you.”xkcd