Convert pandas df to a dictionary

Question

I have a requirement to convert a df that is in following format:

d = {
    'A': ['a1', 'a1', 'a1', 'a1', 'a1', 'a1', 'a1', 'a2', 'a2', 'a2', 'a2', 'a2', 'a2', 'a2', 'a2'],
    'B': ['b1', 'b1', 'b1', 'b1', 'b2', 'b2', 'b2', 'b3', 'b3', 'b3', 'b3', 'b3', 'b3', 'b4', 'b4', ],
    'C': ['c1', 'c2', 'c3', 'c4', 'c5', 'c6', 'c7', 'c8', 'c9', 'c10', 'c11', 'c12', 'c13', 'c14', 'c15', ],
}

df = pd.DataFrame(d)
df
    A   B   C
0   a1  b1  c1
1   a1  b1  c2
2   a1  b1  c3
3   a1  b1  c4
4   a1  b2  c5
5   a1  b2  c6
6   a1  b2  c7
7   a2  b3  c8
8   a2  b3  c9
9   a2  b3  c10
10  a2  b3  c11
11  a2  b3  c12
12  a2  b3  c13
13  a2  b4  c14
14  a2  b4  c15

to a dictionary in following format:

outDict = {
    'a1': {
        'b1': ['c1', 'c2', 'c3', 'c4'],
        'b2': ['c5', 'c6', 'c7'],
    },
    'a2': {
        'b3': ['c8', 'c9', 'c10', 'c11', 'c12', 'c13'],
        'b4': ['c14', 'c15'],
    }
}

i.e. values in column A becomes first level key; values in column B second level keys and values in column C a list.

Any pointers?

Answer 1

Here is another way using pivot_table:

out = {k:v.dropna().to_dict() for k,v in 
      df.pivot_table('C','B','A',aggfunc=list).items()}

---

{'a1': {'b1': ['c1', 'c2', 'c3', 'c4'], 'b2': ['c5', 'c6', 'c7']},
 'a2': {'b3': ['c8', 'c9', 'c10', 'c11', 'c12', 'c13'], 'b4': ['c14', 'c15']}}