Cannot assign a value with python in power query

[Anonymous]

Hello guys, 

I am working on a table in power query. As well, I am using python script from the transform tab. The problem I have occurs when I want to assign a value to a specific column and row in the dataset.

Here is an example:

name	day
max	1
alfred	2

If I want to change the values of the "day" column, I do this:

dataset.iloc[0]["day"] = 0
dataset.iloc[1]["day"] = 0

When Power Query execute the python script, the table didn't change.

Any help?

Thank you!!