Python - Find dictionary keys Present in a Strings List

A dictionary is one of Python's core data types consisting of key-value pairs. A strings list contains elements represented as strings. Python provides several built-in functions like keys(), set(), intersection(), and append() to find dictionary keys that are present in a strings list.

Let's take an example:

• Given dictionary: {'T': 1, 'M': 2, 'E': 3, 'C': 4}
• Given list: ['T', 'A', 'B', 'P', 'E', 'L']
• Result: ['T', 'E']

Key Functions Used

keys() Returns all keys from a dictionary as a view object.

set() Creates a set object to store unique elements and perform set operations.

intersection() Finds common elements between two sets.

append() Adds an element to the end of a list.

Using List Comprehension

List comprehension provides a concise way to iterate through dictionary keys and check if they exist in the string list ?

def dict_keys(d, s):
    return [key for key in d if key in s]

# The input dictionary and string list
dict1 = {'Tablets': 1, 'Mobiles': 2, 'Earbuds': 3, 'Computer': 4}
stng = ['Mouse', 'Hard Drive', 'Pen Drive', 'Earbuds', 'Tablets']

# Calling function
res = dict_keys(dict1, stng)
print("Dictionary keys present in strings list:", res)

Dictionary keys present in strings list: ['Tablets', 'Earbuds']

Using Set and Intersection

This method uses set operations to find common elements between dictionary keys and the string list ?

def dict_keys(d, s):
    return list(set(d.keys()).intersection(s))

# Create the dictionary and string list
dictionary = {'Television': 1, 'Projector': 2, 'White Board': 3}
strings = ['Projector', 'Box', 'Remote']

# Calling function
res = dict_keys(dictionary, strings)
print("Dictionary keys present in strings list:", res)

Dictionary keys present in strings list: ['Projector']

Using For Loop

A traditional approach using a for loop to iterate through dictionary keys and check membership ?

def dict_keys(d_list, s_list):
    avl_keys = []
    for k in d_list:
        if k in s_list:
            avl_keys.append(k)
    return avl_keys

# Create the dictionary and string list
dict1 = {'A': 11, 'B': 12, 'C': 13, 'D': 14, 'E': 15, 'F': 16}
stng = ['M', 'N', 'O', 'E', 'G', 'A', 'C', 'P', 'Q', 'R']

# Calling function
res = dict_keys(dict1, stng)
print("Dictionary keys present in strings list:", res)

Dictionary keys present in strings list: ['A', 'C', 'E']

Using Filter Function

The filter() function with a lambda expression provides a functional programming approach ?

def dict_keys(d, s):
    return list(filter(lambda k: k in s, d))

# Create the dictionary and string list
dcn = {'abc': 10, 'bcd': 20, 'mno': 30, 'xyz': 40, 'pqr': 50}
stng = ['ab', 'mno', 'bcs', 'xy']

# Calling Function
res = dict_keys(dcn, stng)
print("Dictionary keys present in strings list:", res)

Dictionary keys present in strings list: ['mno']

Comparison

Conclusion

Python offers multiple approaches to find dictionary keys present in a strings list. Use set intersection for best performance with large datasets, list comprehension for readable code, and for loops when you need explicit control over the iteration process.