Check value of multidimensional dict (array_column)

Question

I have the necessity to check if a specific value correspond to the value of a multidimensional dict (specifying the key).

multi_dict = [
{'key1': 'value1', 'key2': 'value2', 'key3': 'value3'},
{'key1': 'value10', 'key2': 'value20', 'key3': 'value30'}
]

I'm coming from a PHP environment and I know that there's a function that does that: array_column There's something like this also for Python?

Possible output specifying key1 in order to check if a value correspond:

[value1, value10]

I added a possible output, but mainly I need to check if a static value correspond to the values of a multi dict specifying the key, so if I can return all the values of a specific key in a simple list I can do it easily. — Keaire, Jan 27 '19 at 19:45

score 2 · Accepted Answer · answered Jan 27 '19 at 19:44

You can use a list comprehension:

multi_dict = [
    {'key1': 'value1', 'key2': 'value2', 'key3': 'value3'},
    {'key1': 'value10', 'key2': 'value20', 'key3': 'value30'}
]

result = [d['key1'] for d in multi_dict]
print(result)

Output:

['value1', 'value10']

If you wanted to emulate the third argument of array_column, the index key, you can use dictionary comprehension:

result = {d['key1']: d['key2'] for d in multi_dict}
print(result)

Output:

{'value1': 'value2', 'value10': 'value20'}

Patrick Artner · Answer 2 · 2019-01-27T19:51:45.137

You can extract all values for a key of all dicts:

multi_dict = [ {'key1': 'value1', 'key2': 'value2', 'key3': 'value3'},
               {'key1': 'value10', 'key2': 'value20', 'key3': 'value30'},
               {                   'key2': 'value30', 'key3': 'value40'},
             ]

val_key1 = [d.get('key1') for d in multi_dict] 

print(val_key1)

Output:

['value1', 'value10', None]

You should use dict.get(key) to get a None in case a key is missing.

Doku:

Why dict.get(key) instead of dict[key]? (StackOverflow)
dict.get(key) (python.org)

Check value of multidimensional dict (array_column)

2 Answers2