python - Pivot Pandas dataframe to see if condition is met

Question

I have the following DataFrame that represents whether a User was present in some week, some year:

    User    Year    Week
0   John    2020    1
1   John    2020    2
2   Steve   2020    1
3   Fred    2020    3
4   George  2020    2   
5   George  2020    3
    ...     ...     ...
200 John    2021    2
201 John    2021    4
202 Steve   2021    2
203 Fred    2021    2
204 George  2021    1   
205 George  2021    4

I want to get a DataFrame that groups the dataset by User and each column represents whether he was present in a certain week of a certain year, each column either being of type boolean or integer with possible values 0 or 1.

It would look something like this:

        2020_1  2020_2  2020_3  ... 2021_1  2021_2  2021_3  2021_4
John         1       1       0  ...      0       1       0       1
Steve        1       0       0  ...      0       1       0       0
Fred         0       0       1  ...      0       1       0       0
George       0       1       1  ...      1       0       0       1

Is there anyway to do this without iterating through the DataFrme?

Thanks.

question from:https://stackoverflow.com/questions/65912371/pivot-pandas-dataframe-to-see-if-condition-is-met

Answer 1

Create a new column and use pd.crosstab:

pd.crosstab(df['User'],
            df[['Year','Week']].astype(str).apply('_'.join, axis=1)
           )

Output:

col_0   2020_1  2020_2  2020_3  2021_1  2021_2  2021_4
User                                                  
Fred         0       0       1       0       1       0
George       0       1       1       1       0       1
John         1       1       0       0       1       1
Steve        1       0       0       0       1       0