python - Split dictionary of lists into list of dictionaries

Question

What i need to do is to convert something like this

{'key1': [1, 2, 3], 'key2': [4, 5, 6]}

into

[{'key1': 1, 'key2': 4}, {'key1': 2, 'key2': 5}, {'key1': 3, 'key2': 6}]

The length of the value lists can vary! What's the quickest way to do this (preferably without for loops)?

Answer 1

Works for any number of keys

>>> map(dict, zip(*[[(k, v) for v in value] for k, value in d.items()]))
[{'key2': 4, 'key1': 1}, {'key2': 5, 'key1': 2}, {'key2': 6, 'key1': 3}]

For example:

d = {'key3': [7, 8, 9], 'key2': [4, 5, 6], 'key1': [1, 2, 3]}

>>> map(dict, zip(*[[(k, v) for v in value] for k, value in d.items()]))
[{'key3': 7, 'key2': 4, 'key1': 1}, {'key3': 8, 'key2': 5, 'key1': 2}, {'key3': 9, 'key2': 6, 'key1': 3}]

---

A general solution that works on any number of values or keys: (python2.6)

>>> from itertools import izip_longest
>>> d = {'key2': [3, 4, 5, 6], 'key1': [1, 2]}
>>> map(lambda a: dict(filter(None, a)), izip_longest(*[[(k, v) for v in value] for k, value in d.items()]))
[{'key2': 3, 'key1': 1}, {'key2': 4, 'key1': 2}, {'key2': 5}, {'key2': 6}]

And if you don't have python2.6:

>>> d = {'key2': [3, 4, 5, 6], 'key1': [1, 2]}
>>> map(lambda a: dict(filter(None, a)), map(None, *[[(k, v) for v in value] for k, value in d.items()]))
[{'key2': 3, 'key1': 1}, {'key2': 4, 'key1': 2}, {'key2': 5}, {'key2': 6}]