Python program to convert a list into a list of lists using a step value

When working with lists in Python, you may need to convert a flat list into a list of lists using a specific step value. This allows you to group elements and create nested structures from your data.

Method 1: Using List Slicing with Step Value

The most efficient approach uses list slicing to chunk the original list into smaller sublists ?

def convert_list_with_step(data, step):
    result = []
    for i in range(0, len(data), step):
        result.append(data[i:i+step])
    return result

numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
print("Original list:")
print(numbers)

print("\nConverted with step 3:")
print(convert_list_with_step(numbers, 3))

print("\nConverted with step 2:")
print(convert_list_with_step(numbers, 2))

Original list:
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

Converted with step 3:
[[1, 2, 3], [4, 5, 6], [7, 8, 9], [10]]

Converted with step 2:
[[1, 2], [3, 4], [5, 6], [7, 8], [9, 10]]

Method 2: Using List Comprehension

A more concise approach using list comprehension for the same result ?

def convert_with_comprehension(data, step):
    return [data[i:i+step] for i in range(0, len(data), step)]

fruits = ['apple', 'banana', 'cherry', 'date', 'elderberry', 'fig']
print("Original list:")
print(fruits)

print("\nGrouped by 2:")
print(convert_with_comprehension(fruits, 2))

Original list:
['apple', 'banana', 'cherry', 'date', 'elderberry', 'fig']

Grouped by 2:
[['apple', 'banana'], ['cherry', 'date'], ['elderberry', 'fig']]

Method 3: Converting Individual Strings to Lists

If you need to convert each string element into a separate list ?

def convert_strings_to_lists(data):
    result = []
    for element in data:
        # Split by comma if present, otherwise wrap in list
        if ',' in element:
            sub_list = element.split(', ')
        else:
            sub_list = [element]
        result.append(sub_list)
    return result

names = ['peter', 'king', 'charlie', 'john, doe', 'alice, bob']
print("Original list:")
print(names)

print("\nConverted to list of lists:")
print(convert_strings_to_lists(names))

Original list:
['peter', 'king', 'charlie', 'john, doe', 'alice, bob']

Converted to list of lists:
[['peter'], ['king'], ['charlie'], ['john', 'doe'], ['alice', 'bob']]

Comparison

Conclusion

Use list slicing with step values to group elements efficiently. List comprehension provides the most concise syntax, while string splitting handles comma-separated data within list elements.