Python - Remove keys with substring values

Sometimes, we need to remove keys whose values contain a specific substring. For example, consider the dictionary d = {'name1': 'hello world', 'name2': 'python code', 'name3': 'world peace'}. If we want to remove keys where the value contains the substring 'world', the resulting dictionary should exclude such entries. Let's explore multiple methods to achieve this.

Using Dictionary Comprehension

Using dictionary comprehension is the most efficient method for removing keys with substring values.

# Example
d = {'name1': 'hello world', 'name2': 'python code', 'name3': 'world peace'}
substring = 'world'

# Remove keys where values contain the substring
d = {k: v for k, v in d.items() if substring not in v}

print(d)

{'name2': 'python code'}

Explanation:

• d.items() generates key-value pairs.
• The condition substring not in v filters out keys with values containing the substring.
• A new dictionary is created with the remaining pairs.

Let's explores some more ways to remove keys with substring values in Python dictionaries.

Using del() with for Loop

This method uses for loop to delete keys from the dictionary while iterating over its items.

# Example
d = {'name1': 'hello world', 'name2': 'python code', 'name3': 'world peace'}
substring = 'world'

# Collect keys to remove
keys_to_remove = [k for k, v in d.items() if substring in v]

# Remove the keys
for k in keys_to_remove:
    del d[k]

print(d)

{'name2': 'python code'}

Explanation:

• A list comprehension collects keys where the values contain the substring.
• A loop iterates over these keys, removing them using the del() statement.

Using filter()

This method filters out key-value pairs and reconstructs the dictionary.

# Example
d = {'name1': 'hello world', 'name2': 'python code', 'name3': 'world peace'}
substring = 'world'

# Filter out keys with substring values
d = dict(filter(lambda item: substring not in item[1], d.items()))

print(d)

{'name2': 'python code'}

Explanation:

• filter() iterates through the dictionary items.
• A lambda function ensures only pairs without the substring are retained.
• The dict() function converts the filtered pairs back to a dictionary.

Using a Temporary Dictionary

This method creates a temporary dictionary to store key-value pairs without the substring.

# Example
d = {'name1': 'hello world', 'name2': 'python code', 'name3': 'world peace'}
substring = 'world'

# Create a temporary dictionary
temp = {}
for k, v in d.items():
    if substring not in v:
        temp[k] = v

d = temp

print(d) 

{'name2': 'python code'}

Explanation:

• A temporary dictionary temp is initialized.
• A loop adds key-value pairs without the substring to temp.
• The original dictionary is replaced with temp