How to reference row below in Python Pandas Dataframe?-CodePudding

I have a function that gets the stock price (adjusted closing price) on a specific date of the format DD-MM-YYYY. I have a Pandas Dataframe that looks like the following, with a column for date, as well as the stock price calculated using said function.

         Date  Stock price  Percent change
0  02-07-2022        22.09  
1  06-04-2022        18.22
2  01-01-2022        16.50
3  30-09-2021        18.15
4  03-07-2021        17.96

I need to calculate the percent change, which is calculated by taking (new/old - 1)*100, so in the top cell it would say (22.09/18.22 - 1)*100 = 21.24039517 because the stock increased 21.2% between 06-04-2022 and 02-07-2022.

So I need to "reference" the row below when applying a function, meanwhile I still reference the current row, because I need both to calculate change. For the bottom one, it can just be NaN or similar. Any suggestions?

CodePudding user response：

I would first sort on date (given that that column is already datetime):

df = df.sort_values(by='Date', ascending=True)

And then calculate the percentage change and fill NaN with 0, or with something else if you prefer:

df["Percent change"] = df["Stock price"].pct_change(periods=1).fillna(0)