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pythonpermutationpython-itertools

Permutations of dictionary in python

I have a dictionary like this - 

{'A': 0, 'B': 0, 'C': 0, 'D': 4}

I want to generate a list like this - 

[{'A': 1, 'B': 0, 'C': 0, 'D': 4},
 {'A': 0, 'B': 1, 'C': 0, 'D': 4},
 {'A': 0, 'B': 0, 'C': 1, 'D': 4},
 {'A': 0, 'B': 0, 'C': 0, 'D': 5}]

What is the most pythonic way to do this?

Solution

  • You can use list comprehension and dictionary comprehension together, like this

    d = {'A': 0, 'B': 0, 'C': 0, 'D': 4}
print [{key1: d[key1] + (key1 == key) for key1 in d} for key in d]

    Output

    [{'A': 1, 'B': 0, 'C': 0, 'D': 4},
 {'A': 0, 'B': 0, 'C': 1, 'D': 4},
 {'A': 0, 'B': 1, 'C': 0, 'D': 4},
 {'A': 0, 'B': 0, 'C': 0, 'D': 5}]

    The idea is to generate a new dictionary for each key, and when the key matches the key of the dictionary being constructed with dictionary comprehension, then add 1 to it. (key1 == key) will evaluate to 1 only when both the keys match, otherwise it will be zero.