Initialize a Dictionary with Custom Value list in Python

Initializing a dictionary with custom value lists means creating a dictionary where each key maps to a list containing specific values. This approach is useful when you need to group multiple values under each key or when you want each value to be in list format for further manipulation.

Syntax Overview

Python provides several built-in functions to initialize dictionaries with custom value lists:

• range() - Returns a sequence of numbers
• len() - Returns the length of an object
• zip() - Combines multiple iterables
• dict() - Creates a dictionary
• enumerate() - Iterates with index tracking

Using for Loop

The most straightforward approach uses a for loop to iterate through keys and values, wrapping each value in a list ?

keys = ['P', 'Q', 'R', 'S', 'T']
values = [11, 92, 53, 94, 67]
result = {}

for i in range(len(keys)):
    result[keys[i]] = [values[i]]
    
print("Dictionary with custom value list:")
print(result)

Dictionary with custom value list:
{'P': [11], 'Q': [92], 'R': [53], 'S': [94], 'T': [67]}

Using zip() Function

The zip() function combined with dict() provides a more concise solution ?

keys = ['M', 'N', 'O']
values = [100, 200, 300]

result = dict(zip(keys, [[value] for value in values]))
print("Dictionary using zip():")
print(result)

Dictionary using zip():
{'M': [100], 'N': [200], 'O': [300]}

Using Dictionary Comprehension

Dictionary comprehension offers the most Pythonic and readable approach ?

subjects = ['Math', 'English', 'Hindi', 'Science']
scores = [95, 78, 82, 65]

result = {subjects[i]: [scores[i]] for i in range(len(subjects))}
print("Subject with scores:")
print(result)

Subject with scores:
{'Math': [95], 'English': [78], 'Hindi': [82], 'Science': [65]}

Using enumerate() with zip()

When you need index tracking, combine enumerate() with zip() ?

names = ['John', 'Mark', 'Jonathan', 'Sam', 'Karl']
ages = [18, 26, 22, 24, 33]

result = {name: [age] for i, (name, age) in enumerate(zip(names, ages))}
print("Person name with age:")
print(result)

Person name with age:
{'John': [18], 'Mark': [26], 'Jonathan': [22], 'Sam': [24], 'Karl': [33]}

Comparison of Methods

Conclusion

Dictionary comprehension is the most Pythonic approach for initializing dictionaries with custom value lists. Use zip() for simple mappings, for loops when you need complex logic, and enumerate() when tracking indices is important.