Python>Finding key based on values within a list, from a dictionary

i am using a dict like below and i want a function preferably which returns the key value, based on the value user provides.

test_dict={'Name':[abc,def],'Address':['Local','NonLocal']}

Used the below function:

def find_key_for(input_dict,value):
    result=[]
    for k,v in input_dict.items():
        if value in v:
           result.append(k)
        return result

when i use the above function as below:

print(find_key_for(test-dict,'abc')) it returns [] while i expected Name

alternatively when i do (find_key_for(test-dict,'Local')) it returns [Address] which is expected.

why does it not work for Name? what changes can i make?

Answer

You need to un-indent the return statement:

def find_key_for(input_dict, value):
    result = []
    for k, v in input_dict.items():
        if value in v:
           result.append(k)
    return result

The reason is because if you don’t, and have it inside the for loop, your function will return after only looping once.

Finally, you can use a nested list comprehension in just one line:

test_dict = {'Name': ['abc', 'def'], 'Address': ['Local', 'NonLocal']}

def find_key_for(input_dict, value):
    return [k for k in input_dict if value in input_dict[k]]

print(find_key_for(test_dict, 'abc'))

Or a lambda function:

test_dict = {'Name': ['abc', 'def'], 'Address': ['Local', 'NonLocal']}

find_key_for = lambda input_dict, value: [k for k in input_dict if value in input_dict[k]]

print(find_key_for(test_dict, 'abc'))

Output:

['Name']