python - Combine values of same keys in a list of dicts

Question

I have a list of dictionaries in the following format:

foo = [
    {'a': 'x', 'b': 'y', 'c': 'z'},
    {'a': 'j', 'c': 'z'}
]

I want to group this list of dictionaries into a single dictionary, like:

bar = {
    'a': ['x', 'j'],
    'b': ['y', None],
    'c': ['z', 'z']
}

What I've currently done is, looping through all the dicts in foo and create a list of keys and then looping again over the same to create bar. I wonder whether there is a simpler way to accomplish this. Can anyone help?

Answer 1

bar = {
    k: [d.get(k) for d in foo]
    for k in set().union(*foo)
}

Things to google:

• python list comprehension
• python dict comprehension
• python star
• python dict get
• python set union