Python: How do I multiply DataFrame values by number prior to a certain date-CodePudding

Consider the following DataFrame:

df:
ticker           A        B        C
date
2022-01-02       145      100      100
2022-01-03       450      200      241
2022-01-04       100      200      NaN
2022-01-05       424      324      222
2022-01-06       400      421      320

I want to multiply the values in the columns prior to the date 2022-01-04 (included) for each column as follows:

For column A, I want to multiply by 2

For column B, I want to multiply by 8

For column C, I want to multiply by 4

The resulting DataFrame should look like this:

df2:
ticker           A        B        C
date
2022-01-02       290      800      400
2022-01-03       900      1600     964
2022-01-04       200      1600     NaN
2022-01-05       424      324      222
2022-01-06       400      421      320

How can this be done?

CodePudding user response：

You could do something like this

df.loc[df["ticker date"]<="2022-01-04", ["A", "B", "C"]] = df.loc[df["ticker date"]<="2022-01-04", ["A", "B", "C"]].apply(lambda x: [x["A"]*2, x["B"]*8, x["C"]*4], axis=1, result_type='broadcast')