Python – Test Record existence in Dictionary

Sometimes while working with a pool of records, we can have problems in which we need to check the presence of a particular value of a key for existence. This can have applications in many domains such as day-day programming or web development. Let us discuss certain ways in which this task can be performed.

Method #1 : Using any() + generator expression

The combination of the above functions can be used to perform this task. In this, we simply test for all elements using any(), iterated using generator expression.

Python3

# Python3 code to demonstrate working of
# Test Record existence in Dictionary
# Using any() + generator expression

# initializing list
test_list = [{'name': 'Nikhil', 'age': 22},
             {'name': 'Akshat', 'age': 23},
             {'name': 'Akash', 'age': 23}]

# printing original list
print("The original list is : " + str(test_list))

# initializing key and value
test_key = 'name'
test_val = 'Nikhil'

# Test Record existence in Dictionary
# Using any() + generator expression
res = any(sub[test_key] == test_val for sub in test_list)

# printing result
print("Does key value contain in dictionary list : " + str(res))

Output : 
The original list is : [{‘name’: ‘Nikhil’, ‘age’: 22}, {‘name’: ‘Akshat’, ‘age’: 23}, {‘name’: ‘Akash’, ‘age’: 23}] 
Does key value contain in dictionary list : True 

Method #2 : Using filter() + lambda 

The combination of the above functions can be used to perform this task. In this, we check for all values using filter and iteration using lambda function.

Python3

# Python3 code to demonstrate working of
# Test Record existence in Dictionary
# Using filter() + lambda

# initializing list
test_list = [{'name': 'Nikhil', 'age': 22},
             {'name': 'Akshat', 'age': 23},
             {'name': 'Akash', 'age': 23}]


# printing original list
print("The original list is : " + str(test_list))

# initializing key and value
test_key = 'name'
test_val = 'Nikhil'

# Test Record existence in Dictionary
# Using filter() + lambda
res = filter(lambda sub: test_val in sub.values(), test_list)
if len(list(res)):
    res = True
else:
    res = False

# printing result
print("Does key value contain in dictionary list : " + str(res))

Output : 
The original list is : [{‘name’: ‘Nikhil’, ‘age’: 22}, {‘name’: ‘Akshat’, ‘age’: 23}, {‘name’: ‘Akash’, ‘age’: 23}] 
Does key value contain in dictionary list : True 

Method #3 : Using keys() method

Python3

# Python3 code to demonstrate working of
# Test Record existence in Dictionary

# initializing list
test_list = [{ 'name' : 'Nikhil', 'age' : 22},
            { 'name' : 'Akshat', 'age' : 23},
            { 'name' : 'Akash', 'age' : 23}]


# printing original list
print("The original list is : " + str(test_list))

# initializing key and value
test_key = 'name'
test_val = 'Nikhil'

# Test Record existence in Dictionary
res=False
for i in test_list:
    if test_key in i.keys() and i[test_key]==test_val:
        res=True
# printing result
print("Does key value contain in dictionary list : " + str(res))

Output

The original list is : [{'name': 'Nikhil', 'age': 22}, {'name': 'Akshat', 'age': 23}, {'name': 'Akash', 'age': 23}]
Does key value contain in dictionary list : True