Python | Test if element is dictionary value

Sometimes, while working with a Python dictionary, we have a specific use case in which we just need to find if a particular value is present in the dictionary as it's any key's value. This can have use cases in any field of programming one can think of. Let's discuss certain ways in which this problem can be solved using Python. 

Check if a value exists in the dictionary using any() function

This is the method by which this problem can be solved. In this, we iterate through the whole dictionary using list comprehension and check for each key's values for a match using a conditional statement. 

test_dict = {'gfg': 1, 'is': 2, 'best': 3}

# Check if key exist in dictionary using any()
if any([True for k,v in test_dict.items() if v == 21]):
    print(f"Yes, It exists in dictionary")
else:
    print(f"No, It doesn't exists in dictionary")
    

No, It doesn't exists in dictionary

Check if a value exists in the dictionary using a loop 

This is the brute way in which this problem can be solved. In this, we iterate through the whole dictionary using loops and check for each key's values for a match using a conditional statement. 

# initializing dictionary
test_dict = {'gfg' : 1, 'is' : 2, 'best' : 3}

# printing original dictionary
print("The original dictionary is : " + str(test_dict))

# Test if element is dictionary value
# Using loops
res = False
for key in test_dict:
    if(test_dict[key] == 3):
        res = True
        break

# printing result
print("Is 3 present in dictionary : " + str(res))

Output :

The original dictionary is : {'best': 3, 'is': 2, 'gfg': 1}
Is 3 present in dictionary : True

Time complexity: O(N), where N is the number of key-value pairs in the dictionary. 
Auxiliary space: O(1).

Check if a value exists in the dictionary using in operator and values() 

This task can be performed by utilizing the above functionalities. The in operator can be used to get the true value of presence and the values function is required to extract all values of dictionaries. 

# initializing dictionary
test_dict = {'gfg' : 1, 'is' : 2, 'best' : 3}

# printing original dictionary
print("The original dictionary is : " + str(test_dict))

# Test if element is dictionary value
# Using in operator and values()
res = 3 in test_dict.values()

# printing result
print("Is 3 present in dictionary : " + str(res))

Output :

The original dictionary is : {'best': 3, 'is': 2, 'gfg': 1}
Is 3 present in dictionary : True

Time Complexity: O(n), where n is the number of values in the dictionary test_dict. 

Auxiliary Space: O(1), as no extra space is used.

Using the get() method of a dictionary

The get() method returns the value for a given key if it exists in the dictionary. If the key does not exist, it returns None. You can use this behavior to check if a value exists in the dictionary by checking if it is in the list returned by values().

test_dict = {'gfg': 1, 'is': 2, 'best': 3}

if 21 in test_dict.values():
    print(f"Yes, It exists in dictionary")
else:
    print(f"No, It doesn't exist in dictionary")

No, It doesn't exist in dictionary

Time complexity: O(n)
Auxiliary space: O(1)

Using isinstance() function:

Approach:

Check if the input value is of dictionary type or not.
If it is, check if the given element exists in any of the dictionary values.
If yes, return True. Else, return False.

def check_dict_value_1(d, val):
    if isinstance(d, dict):
        return any(val == v for v in d.values())
    return False
my_dict = {'a': 1, 'b': 2, 'c': {'d': 3, 'e': 4}, 'f': 5}
my_value = 4
result = check_dict_value_1(my_dict, my_value)
print(result)

False

Time Complexity: O(n)
Auxiliary Space: O(1)