CODEWITHSUNDEEP
pythonpython-2.7dictionary-comprehension
user2242044
user2242044

Reputation: 9213

Breaking down list of list into dictionaries

I have a list of list, s, that is the result of querying a database on Fruit, item[0] is the name of the fruit, item[1] is the whether or not the fruit has seeds, and item[2] is whether or not it's edible.

s = [['Apple','Yes','Edible'], ['Watermellon','Yes','Yes']]

As my actual list is much bigger, I would like a really easy way to reference/return these values. For example, print my_dict['Apple']['Seeds'] would yield Yes

I think my best option would be to create a dictionary, but am looking for recommendations on if this is a good method and how to do this.

I started writing some code but am not sure how to get the second set of headers in place, so my example uses an index instead.

my_dict =  {t[0]:t[1:] for t in s}

print my_dict['Apple'][0]

Upvotes: 0

Views: 65

Answers (3)

Rafael Lerm
Rafael Lerm

Reputation: 1400

If the second set of keys never changes, it would be better to define a proper object with fields. This might seem overkill or to verbose, but there is always collections.namedtuple to help.

namedtuple creates a new class from a list of field names. That class also supports being initialized by a list. To use your example:

import collections

Fruit = collections.namedtuple('Fruit', ['name', 'seeds', 'edible'])

This way, you can easily create Fruit objects from a list:

f = Fruit('Apple', True, False)
# Or, if you already have a list with the values
params = ['Apple', True, False]
f = Fruit(*params)

print f.seed

So you can create a list of fruits in a very easy way:

s = [['Apple','Yes','Edible'], ['Watermellon','Yes','Yes']]

fruits = [Fruit(*l) for l in s]

You really need to have a dictionary indexed by a certain field, it is not much different:

s = [['Apple','Yes','Edible'], ['Watermellon','Yes','Yes']]

fruit_dict = {l[0]: Fruit(*l) for l in s}    
print(fruit_dict['Apple'].seeds)

namedtuples can be very convenient when transforming lists of values into more easy to use objects (such as when reading a CSV file, which is a case very similar to what you are asking).

Upvotes: 2

Malik Brahimi
Malik Brahimi

Reputation: 16711

import copy

def list_to_dict(lst):
    local = copy.copy(lst) # copied lst to local
    fruit = [i.pop(0) for i in local] # get fruit names

    result = {}
    for i in range(len(local)):
        result[fruit[i]] = local[i]
    return result

This returns the dictionary you want.

Upvotes: 0

lopar
lopar

Reputation: 2442

fruit_map = {
    fruit: {'Seeds': seeds, 'Edible': edible} for fruit, seeds, edible in s}

Upvotes: 5

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