How can I do reversed dictionary for every value and a key in python?-CodePudding

I am trying to convert this dictionary:

dict1={x: ['John', 'Jack'], y: ['Julia', 'Michael']}

to this form:

 dict2={'Julia': y, 'John': x,  'Jack': x, 'Michael': y}

I researched that a lot but I could not find anything.How can I do that?

CodePudding user response：

Easy as pie using a Dictionary Comprehension:

dict1 = {'x': ['John', 'Jack'], 'y': ['Julia', 'Michael']}
dict2 = {'Julia': 'y', 'John': 'x',  'Jack': 'x', 'Michael': 'y'}
dict3 = {
    elem: key
    for key, list_value in dict1.items()
    for elem in list_value
}
assert dict2 == dict3

You're welcome. However, please not that if one of the letters appear in several lists, only the last occurrence will be taken into account, for example:

dict1 = {'x': ['Jack'], 'y': ['Jack']}
dict3 = {
    elem: key
    for key, list_value in dict1.items()
    for elem in list_value
}
print(dict3)  # {'Jack': 'y'}

CodePudding user response：

This is a simple operation, and it is not recommended to use multi-loop dictionary analysis. In general, you should try to keep the code simple and easy to read when it is not necessary. If there is a key conflict between the dictionaries, you should also write comments to ensure that others can fully understand.

new_dict = {}
for value, keys in dict1.items():
    for key in keys:
        new_dict[key] = value

CodePudding user response：

You can first get all the values from dict1 as your new keys then iterate over the dict1 and test if you key exists in the values of key-dict1.

keys = [element for val in list(dict1.values()) for element in val]
dict2 = dict()
for key in dict1.keys():
    for k in keys:
        if k in dict1.get(key):
            dict2[k] = key
dict2

output

{'Julia': y, 'John': x,  'Jack': x, 'Michael': y}

CodePudding user response：

Alternatively, you can use itertools:

import itertools

dict2 = dict(itertools.chain.from_iterable([zip(v,len(v)*k) for k, v in dict1.items()]))