Python Pandas - Select first periods of time series data based on a date offset

To select first periods of time series based on a date offset, use the first() method. At first, set the date index with periods and freq parameters. Freq is for frequency −

i = pd.date_range('2021-07-15', periods=5, freq='3D')

Now, create a DataFrame with above index −

dataFrame = pd.DataFrame({'k': [1, 2, 3, 4, 5]}, index=i) 

Fetch rows from first 4 days i.e. 4D −

dataFrame.first('4D')

Example

Following is the complete code −

 import pandas as pd # date index set with 5 periods and frequency of 3 days i = pd.date_range('2021-07-15', periods=5, freq='3D') # creating DataFrame with above index dataFrame = pd.DataFrame({'k': [1, 2, 3, 4, 5]}, index=i) print"DataFrame...\n",dataFrame # fetching initial few rows # fetch rows from the first 4 days print"First few rows fetched..\n",dataFrame.first('4D');

Output

This will produce the following output −

DataFrame...              k 2021-07-15   1 2021-07-18   2 2021-07-21   3 2021-07-24   4 2021-07-27   5 First few rows fetched..             k 2021-07-15   1 2021-07-18 2