Python search by value

Question

I need a proper solution to search for a key in a nested data structures in Python. Lets assume that I have variable with value 'check' and dict like this:

SERVICES = {
    'domain': ['check','whois','register'],
    'user': ['create','show','delete'],
    'invoice': ['toPdf','print']
}

What is the best way to check in which array-key is the 'check' value and return 'domain'?

Answer 1

Standard approach:

for k, v in SERVICES.items(): # or iteritems in Python 2
    if 'check' in v:
        print(k) # 'domain'
        break

If you expect to have multiple keys matching the condition, just remove break.

Functional approach:

>>> next(filter(lambda x: 'check' in SERVICES[x], SERVICES))
'domain'

Answer 2

Simply iterate over the dictionary keys and check if check is one of the values of the value corresponding to the key. If you find it then give it to the next call.

print next(key for key in SERVICES if 'check' in SERVICES[key])
# domain