I try to filter a dataframe using the following expression: I am seeking the times “col” changes to “val”:

filtered_df = df[(df[col]== val) & (df.shift(1)[col] != df[col])]

df is a dataframe that is generated by a function: df= create_df(data)

The filtered_df is empty even though there condition is verified at least one time in my data.

When I try to export my df to a csv file:

data = pd.to_csv("out") then

Apply the above filter to data, it works, I get a non empty dataframe.

I don’t know how to explain this , “df” and “data” are meant to be the same.

Any help please? Thanks9