Python - Remove Keys with K value

We are given a dictionary we need to remove the keys with K value. For example, we are having a dictionary d = {'a': 1, 'b': 2, 'c': 1, 'd': 3} we need to remove the keys which is having K value so that the output should be {'b': 2, 'd': 3} . We can use dictionary comprehension and many other methods to remove keys.

Using Dictionary Comprehension

We can use dictionary comprehension to create a new dictionary excluding the key-value pairs with the specified value.

d = {'a': 1, 'b': 2, 'c': 1, 'd': 3}
K = 1

# Dictionary comprehension to create a new dictionary excluding keys with value equal to K
res = {key: value for key, value in d.items() if value != K}
print(res)

{'b': 2, 'd': 3}

Explanation:

• Dictionary Comprehension Iterates through each key-value pair in dictionary d and includes only pairs where the value is not equal to K (which is 1 in this case).
• Resulting Dictionary new dictionary res contains filtered key-value pairs where the value is not equal to K effectively removing all keys with the value 1

Using dict.items()

Iterate through dictionary and remove keys with the value K by using the del statement.

d = {'a': 1, 'b': 2, 'c': 1, 'd': 3}
K = 1

# Create a list of keys where the value is equal to K (value to be removed)
k = [key for key, value in d.items() if value == K]

# Iterate through the list of keys to remove and delete them from the dictionary
for key in k:
    del d[key]
print(d)

{'b': 2, 'd': 3}

Explanation:

• Identify Keys to Remove list comprehension creates a list k containing the keys where value is equal to K (1), which are the keys 'a' and 'c'.
• Remove Keys from Dictionary for loop iterates through the list k and removes the corresponding key-value pairs from the dictionary d using the del statement.

Using filter() and lambda

We can use the filter() function in combination with a lambda expression to filter out keys with value K.

d = {'a': 1, 'b': 2, 'c': 1, 'd': 3}
K = 1

# Use the filter function to filter out items with value equal to K
# The lambda function checks if the value is not equal to K
res = dict(filter(lambda item: item[1] != K, d.items()))

print(res)

{'b': 2, 'd': 3}

Explanation:

• filter() Function filters the items in the dictionary d by applying the lambda function, which checks whether the value is not equal to K (1).
• dict() Conversion filter() function returns an iterable so dict() is used to convert it back into a dictionary resulting in res containing only key-value pairs where value is not equal to K.

Using collections.defaultdict

This approach can be helpful if you're working with defaultdict and need to maintain some default behavior

from collections import defaultdict

# Initial defaultdict with default value as int (0) and some key-value pairs
d = defaultdict(int, {'a': 1, 'b': 2, 'c': 1, 'd': 3})
K = 1  # Value to be removed from the dictionary

# Dictionary comprehension to create a new dictionary excluding keys with value equal to K
res = {key: value for key, value in d.items() if value != K}
print(res)

{'b': 2, 'd': 3}

Explanation:

• Create a defaultdict and Filter Keys defaultdict is created with a default value of 0 and some predefined key-value pairs. Then a dictionary comprehension filters out key-value pairs where the value equals K (which is 1).
• Resulting Dictionary resulting dictionary res contains only the key-value pairs where the value is not equal to K effectively removing all keys with value 1.