Categorizing data in dataframe

I have a dataframe named AH, with columns F1 and F2:

F1      F2
aq      ab
ac      my

(and so on)

I wanted to make another column and classify each column first so it will become:

F1  Category1    F2    Category2
aq     77        ab     11
ac     77        my     55

The data are preprocessed already and I have made this code:

for len in range (AH):

    if AH ['F1'] =={'aq','ac'}:
        AH.loc[index, 'Category1'] = '77'
    elif AH ['F2'] =={'ab'}:
        AH.loc[index, 'Category1'] = '11'
    elif AH ['F2'] =={'my'}:
        AH.loc[index, 'Category1'] = '55'
   else:
        'NaN'

However, the error showed:

TypeError: 'DataFrame' object cannot be interpreted as an integer
    

Anyone who can answer?