How to generate a list of dictionaries from a list of keys and the same value

Question

I would like to create a list of dicts from a list of keys and with the same value for each dict.

The structure would be:

[{key1: value}, {key2: value}, {key3: value}, ...]

I begin with a list of keys:

my_list = [3423, 77813, 12, 153, 1899]

Let's say the value would be ['dog', 'cat'].

Here is what the final result should look like:

[{3423:['dog', 'cat']}, {77813:['dog', 'cat']}, {12:['dog', 'cat']},
 {153:['dog', 'cat']}, {1899:['dog', 'cat']}]

Answer 1

If you want something really simple, you can use a list comprehension:

data = ['dog', 'cat']

my_list = [3423, 77813, 12, 153, 1899]

result = [{k:data} for k in my_list]

print(result)
# [{3423: ['dog', 'cat']}, {77813: ['dog', 'cat']}, {12: ['dog', 'cat']}, {153: ['dog', 'cat']}, {1899: ['dog', 'cat']}]

Additionally, here is an example of adding/removing values with the very convienient defaultdict:

from collections import defaultdict

my_list = [3423, 77813, 12, 153, 1899]

new_list = []
for number in my_list:

    # create the defaultdict here
    d = defaultdict(list)

    # add some data
    d[number] += ['dog', 'cat', 'kitten']

    # remove some data
    d[number].remove('kitten')

    # append dictionary
    new_list.append(dict(d))

print(new_list)

Which outputs:

[{3423: ['dog', 'cat']}, {77813: ['dog', 'cat']}, {12: ['dog', 'cat']}, {153: ['dog', 'cat']}, {1899: ['dog', 'cat']}]

Using a defaultdict here is helpful, as it initializes each entry in the dictionary with an empty list. If you don't want to do this, you could achieve this with a normal dictionary, as shown in your question, but this requires you to initialize the empty lists yourself.