Finding a key value pair in a dictionary that contains a specific value in python

Question

In python 3 and python 2, is there a way to get the key value pair in a dictionary that contains a specific value? Eg here is the dictionary:

dict_a = {'key_1': [23, 'ab', 'cd'], 'key_2': [12, 'aa', 'hg']}

How do I get the key value pair where 'cd' is present in the value? I tried using itervalues() but that does not seem to work

Answer 1

You can use a simple dictionary comprehension to check if cd is in the value of each key, value pair:

>>> dict_a = {'key_1': [23, 'ab', 'cd'], 'key_2': [12, 'aa', 'hg']}
>>> {k: v for k, v in dict_a.items() if 'cd' in v}
{'key_1': [23, 'ab', 'cd']}

This can be generalized by extracting the logic into a function:

>>> def filter_dict(d, key):
    return {k: v for k, v in d.items() if key in v}

>>> dict_a = {'key_1': [23, 'ab', 'cd'], 'key_2': [12, 'aa', 'hg']}
>>> filter_dict(dict_a, 'cd')
{'key_1': [23, 'ab', 'cd']}
>>>

Answer 2

Iterate over all the items in the dict

dict_a = {'key_1': [23, 'ab', 'cd'], 'key_2': [12, 'aa', 'hg']}
for k, v in dict_a.iteritems():
    if 'cd' in v:
        print k, v

key_1 [23, 'ab', 'cd']

Answer 3

You can simply loop through your dictionary items and check if your value is in the value, eg:

for k, v in dict_a.items():  # use iteritems() on Python 2.x
    if "cd" in v:
        print("key: {}, value: {}".format(k, v))

Answer 4

You can write your own small method to check a value in the dictionary.

dict_a = {'key_1': [23, 'ab', 'cd'], 'key_2': [12, 'aa', 'hg']}

def checkValue(dictionary, value):
    for key, valueList in dict_a.items():
        if value in valueList:
            print("value(" + value + ") present in " + str(valueList) + " with key (" + key + ")")
            break

checkValue(dict_a, 'cd')

Sample Run

value(cd) present in [23, 'ab', 'cd'] with key (key_1)