Python – Performs calculation/arithmetic operations on two fields in the Pandas Dataframe constructor

I need to simulate some trading data using numpy and pandas, similar to the code below:

import random
import numpy as np
import pandas as pd
n=1000

sample_df = pd. DataFrame({ 
'arrival_date':np.random.choice( pd.date_range('1/1/2015', periods=n, 
                      freq='D'), n),
'days_stay': [random.randint(1,14) for x in range(n)]
})

The dataframe needs to have 3 fields, two of which are calculated similar to the above, plus another date field that adds the values of the two fields:

'departure_date': 'arrival_date' + 'days_stay'

Note that I prefer to define all three fields in the pandas data frame constructor instead of having to define a function for the last field and then reference it in the second data frame step to get the data.

sample_df = pd. DataFrame({ 
'arrival_date':np.random.choice( pd.date_range('1/1/2015', periods=n, 
                      freq='D'), n),
'days_stay': [random.randint(1,14) for x in range(n)],
'departure_date': 'arrival_date' + 'days_stay'
})

Is this possible?

Thanks in advance.

Try the following. In PD. Using assign on Dataframe() we can use the created df and its data and assign a new column.

sample_df = pd. DataFrame({ 
'arrival_date':np.random.choice( pd.date_range('1/1/2015', periods=n, 
                      freq='D'), n),
'days_stay': [random.randint(1,14) for x in range(n)],
}).assign(departure_date = lambda x: x.arrival_date + x.days_stay.apply(lambda x: pd. Timedelta(str(x)+'D')))

Sample output:

    arrival_date   days_stay    departure_date
0   2015-02-17     3            2015-02-20
1   2015-01-18     13           2015-01-31
2   2015-02-12     6            2015-02-18
3   2015-01-15     14           2015-01-29
4   2015-03-11     5            2015-03-16