Question

I have a huge dictionary something like this:

d[id1][id2] = value

example:

books["auth1"]["humor"] = 20
books["auth1"]["action"] = 30
books["auth2"]["comedy"] = 20

and so on..

Each of the “auth” keys can have any set of “genres” associated wtih them. The value for a keyed item is the number of books they wrote.

Now what I want is to convert it in a form of matrix…something like:

                    "humor"       "action"        "comedy"
      "auth1"         20            30               0
      "auth2"          0            0                20

How do i do this?
Thanks

Answer 1

Use a list comprehension to turn a dict into a list of lists and/or a numpy array:

np.array([[books[author][genre] for genre in sorted(books[author])] for author in sorted(books)])

EDIT

Apparently you have an irregular number of keys in each sub-dictionary. Make a list of all the genres:

genres = ['humor', 'action', 'comedy']

And then iterate over the dictionaries in the normal manner:

list_of_lists = []
for author_name, author in sorted(books.items()):
    titles = []
    for genre in genres:
        try:
            titles.append(author[genre])
        except KeyError:
            titles.append(0)
    list_of_lists.append(titles)

books_array = numpy.array(list_of_lists)

Basically I’m attempting to append a value from each key in genres to a list. If the key is not there, it throws an error. I catch the error, and append a 0 to the list instead.