Construct pandas DataFrame from items in nested dictionary

Question

Suppose I have a nested dictionary \'user_dict\' with structure:

• Level 1: UserId (Long Integer)
• Level 2: Category (S

Answer 1

pd.concat accepts a dictionary. With this in mind, it is possible to improve upon the currently accepted answer in terms of simplicity and performance by use a dictionary comprehension to build a dictionary mapping keys to sub-frames.

pd.concat({k: pd.DataFrame(v).T for k, v in user_dict.items()}, axis=0)

Or,

pd.concat({
        k: pd.DataFrame.from_dict(v, 'index') for k, v in user_dict.items()
    }, 
    axis=0)

              att_1     att_2
12 Category 1     1  whatever
   Category 2    23   another
15 Category 1    10       foo
   Category 2    30       bar