Get key if element matches one of the list items-CodePudding

I have a dictionary that has list of strings as values:

components = {
    'skin': [
        'first',
        'second',
        'third',
    ],
    'hair': [
        'fourth',
        'fifth',
    ]
}

I want to return the key if a matching string was found in all of the lists, i.e.:

fourth -> returns hair

second -> returns skin

etc.

CodePudding user response：

Try this:

>>> def fnd_key(dct, srch_wrd):
...    for k,v in dct.items():
...        if srch_wrd in v:
...            return k

>>> components = {'skin': ['first', 'second', 'third'], 'hair': ['fourth','fifth']}

>>> fnd_key(components, 'second')
'skin'

>>> fnd_key(components, 'fourth')
'hair'

You can try this if value (like:second) exist in multi list:

>>> def fnd_key(dct, srch_wrd):
...    for k,v in dct.items():
...        if srch_wrd in v:
...           yield k

>>> components = {'skin': ['first', 'second', 'third'], 
                  'hair': ['fourth','fifth', 'second']}
>>> for ky in fnd_key(components, 'second'):
...    print(ky)

skin
hair

CodePudding user response：

Use the in keyword.

for key in components.keys():
    if search in components[key]:
        print(key)

Beware that, the time complexity of in depends on the container.

list - Average: O(n)
set/dict - Average: O(1), Worst: O(n)

CodePudding user response：

print([k for k,v in components.items() if 'fourth' in v][0])

CodePudding user response：

You could write a search algorithm but repeating the search many times is inefficient. If your values in the sublists are unique, you should reverse and flatten your dictionary.

>>> components_rev = {v:k for k, values in components.items() for v in values}
>>> components_rev
{'first': 'skin', 'second': 'skin', 'third': 'skin', 'fourth': 'hair', 'fifth': 'hair'}
>>> components_rev['fourth']
'hair'

CodePudding user response：

Try this

components = {
    'skin': [
        'first',
        'second',
        'third',
        ],
    'hair': [
        'fourth',
        'fifth',
    ]
}

def find_key(myDict, value):
    for key in myDict:
        if value in myDict[key]:
            return key
    return -1
    
print(find_key(components, 'fourth'))

CodePudding user response：

for example you can do something like this if you wanted to make a dictionary of key value of pairs like: 'found item': 'key for found item'

but like many said you might need to find a better structure than list if you are working with really big data or something. but unless the data really is huge i doubt there will be any real problem

products = {
        'electronics': [
            'laptop',
            'tv',
            'monitor'
            ],
        'food': [
            'doritos',
            'mac n cheese'
            ]
        }

# words to look for = 'mac n cheese', 'tv'
words = ['mac n cheese', 'tv']

found_words = {}

# for every key in components ('electronics', 'food')
for product_type_key in products.keys():
    # for each item in components[key] in this case list
    for product in products[product_type_key]:
        if product in words:
            print(f"{product} found in products['{product_type_key}']")
            found_words[product] = f'was found in {product_type_key}'

print('\n')
print("found_words:")
for k, v in found_words.items():
    print(f"{k}: {v}")

output:

tv found in products['electronics']
mac n cheese found in products['food']


found_words:
tv: was found in electronics
mac n cheese: was found in food