Python | Check if tuple exists as dictionary key

Sometimes, while working with dictionaries, there is a possibility that it’s keys be in form of tuples. This can be a sub problem to some of web development domain. Let’s discuss certain ways in which this problem can be solved. 

Method #1 : Using in operator This is the most recommended and Pythonic way to perform this particular task. It checks for particular tuple and returns True in case of it occurs or False if doesn’t. 

The original dictionary : {(3, 4): 'gfg', 6: 'is', (9, 1): 'best'}
Does tuple exists as dictionary key ? : False

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

Method #2 : Using get() We can use dictionary’s get(), which searches for key in dictionary and if it doesn’t get it, it returns a None. This can be extended in case of tuple keys as well. 

The original dictionary : {(3, 4): 'gfg', (9, 1): 'best', 6: 'is'}
Does tuple exists as dictionary key ? : False

Method #3: Using try-catch

Using try-catch, initializes a dictionary, prints the original dictionary,initializes a target tuple and uses try-catch block to check if the target tuple exists as a key in the dictionary. If it does exist, it sets the variable “res” to True, otherwise it sets it to False. The try-catch block will raise a KeyError when the key is not found in the dictionary, and this KeyError is caught and the variable “res” is not modified so it stays False.

The original dictionary : {(3, 4): 'gfg', 6: 'is', (9, 1): 'best'}
Does tuple exists as dictionary key ? : False

This method has a time complexity of O(1) as the try-catch block will only be executed once and the dictionary key access is O(1) operation in average case. The auxiliary space of this method is O(1) as it only uses a single variable “res” to store the result.

Method #4: Using the “in” keyword with dictionary keys()

we use the “in” keyword to check if the “tar_tup” tuple exists in the keys of the “test_dict” dictionary. We assign the resulting boolean value to the “res” variable and print it out. In this case, the tuple (3, 5) does not exist as a key in the dictionary, so the result is False.

The original dictionary : {(3, 4): 'gfg', 6: 'is', (9, 1): 'best'}
Does tuple exists as dictionary key ? : False

Time complexity: O(1) 
Auxiliary Space: O(1)

Method #5: Using the dictionary.items() inbuilt methods :

So we are iterating through the dictionary using test_dict.items() and we are also using in keyword to check whether the tuple tar_tup is there in the dictionary. If it is there we return TRUE else return FALSE.

The original dictionary : {(3, 4): 'gfg', 6: 'is', (9, 1): 'best'}
Does tuple exists as dictionary key ? : False

Time complexity: O(1) 
Auxiliary Space: O(1) as no extra memory is used

Method #6: Using a list comprehension to check if the tuple is equal to any of the dictionary keys:

Step by step Algorithm:

1. Create a dictionary test_dict with key-value pairs.
2. Print the original dictionary.
3. Create a target tuple tar_tup.
4. Use any function with a generator expression to check if the tar_tup exists as a key in the dictionary.
5. Print the result.

The original dictionary : {(3, 4): 'gfg', 6: 'is', (9, 1): 'best'}
Does tuple exists as dictionary key ? : False

Time Complexity: O(n), where n is the number of keys in the dictionary, This is because the time complexity of this algorithm depends on the size of the input dictionary and the size of the target tuple.
Auxiliary Space: O(1), This is because it only requires a fixed amount of memory to store the input dictionary and the target tuple, regardless of their sizes.

Method #7: Using a loop to iterate through the dictionary keys and compare them with the target tuple.

The original dictionary : {(3, 4): 'gfg', 6: 'is', (9, 1): 'best'}
Does tuple exists as dictionary key ? : False

Time complexity: O(1) 
Auxiliary Space: O(1) as no extra memory is used