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Oct 29, 2023 2 mins

Shorten a Python List to a Specific Length

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Python being a versatile programming language, provides multiple ways to manipulate lists efficiently. If you find yourself with a list containing more elements than needed and want to shorten it to a specific length, there are several approaches at your disposal. In this article, we will explore four different methods to achieve this task, along with examples and explanations.

Slicing

Slicing is a concise and Pythonic way to extract a portion of a list. To shorten a list to a specific length, you can use slicing with the [:n] syntax, where n represents the desired length. Let’s consider an example.

original_list = [10, 20, 30, 40, 50, 60, 70, 80, 90, 100]
shortened_list = original_list[:6]

print(shortened_list) # [10, 20, 30, 40, 50, 60]

In this example, original_list[:6] extracts the first 6 elements of the original list, creating a shortened version.

List Comprehension

List comprehension is a concise and powerful feature in Python, allowing you to create a new list based on an existing one. To shorten a list, you can use list comprehension to iterate over the desired number of elements. Here’s an example:

original_list = [10, 20, 30, 40, 50, 60, 70, 80, 90, 100]
shortened_list = [x for x in original_list[:6]]

print(shortened_list) # [10, 20, 30, 40, 50, 60]

In this example, the list comprehension [x for x in original_list[:6]] achieves the same result as the slicing approach, creating a new list with the first 6 elements.

Using del Statement

The del statement in Python is not only used to delete variables but also elements from a list. To shorten a list, you can use del to remove elements beyond the desired length. Here’s how you can do it:

original_list = [10, 20, 30, 40, 50, 60, 70, 80, 90, 100]
del original_list[6:]

print(original_list) # [10, 20, 30, 40, 50, 60]

In this example, del original_list[6:] removes elements starting from index 6 until the end of the list, effectively shortening it to the desired length.

Using pop() Method:

The pop() method is used to remove and return an element from a specific index in a list. By using a loop and the pop() method, you can iteratively shorten the list to the desired length. Here’s an example:

original_list = [10, 20, 30, 40, 50, 60, 70, 80, 90, 100]
while len(original_list) > 6:
    original_list.pop()

print(original_list) # [10, 20, 30, 40, 50, 60]

In this example, the while loop continues to pop() elements from the end of the list until its length becomes 6, achieving the desired result.

Conclusion

Shortening a Python list to a specific length can be accomplished using various approaches, each with its own advantages. Whether you prefer the simplicity of slicing, the elegance of list comprehension, the directness of the del statement, or the flexibility of the pop() method, Python offers multiple tools to cater to your specific needs. Understanding these techniques empowers you to manipulate lists effectively and write more concise and readable code.


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