highlighting maximum value dataframe

[PolskaYBZ]

Hello,

I am reading through a book about data analysis where I got stuck with an excercice in which I need to highlight the maximum value of each column in a pandas Dataframe.



After I removed all the unneccesary data in a Dataframe, I need to perform the last 3 steps ;


1. Use the idxmax method to find the index label of the maximum value for each column.

max_cols = college_n2.idxmax()
max_cols

Output:
SATVRMID           California Institute of Technology
SATMTMID           California Institute of Technology
UGDS               University of Phoenix-Arizona
UGDS_WHITE         Mr Leon's School of Hair Design-Moscow
...
PCTFLOAN           ABC Beauty College Inc
UG25ABV            Dongguk University-Los Angeles
MD_EARN_WNE_P10    Medical College of Wisconsin
GRAD_DEBT_MDN_SUPP Southwest University of Visual Arts-Tucson

Length: 18, dtype: object

2. Call the unique method afterwards on the max_cols Series,

unique_max_cols = max_cols.unique()
unique_max_cols[:5]

Output:
array(['California Institute of Technology',
'University of Phoenix-Arizona',
"Mr Leon's School of Hair Design-Moscow",
'Velvatex College of Beauty Culture',
'Thunderbird School of Global Management'], dtype=object)

3. Afterwards, the values of unique_max_cols will be passed in the dataframe to select and highlight the maximum value.

college_n2.loc[unique_max_cols].style.highlight_max()

I understand the first step, but I do not fully understand why in step 2 I need to select only the unique values and how then anyway in step 3 they are able to select the maximum values.

Some clarification would be much appreciated.

Thank you.