5 Best Ways to Return the Length of String Array Elements in Python

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πŸ’‘ Problem Formulation: Python developers often need to process arrays of strings and retrieve the length of each element within them. Consider a list of names, ['Alice', 'Bob', 'Charlie'], where the task is to output the corresponding lengths of these names, ideally in the form of an integer array like [5, 3, 7].

Method 1: Using a For Loop

The for loop method involves iterating through the array, measuring the length of each string with the built-in len() function, and adding the length to a new list. This method is straightforward and easy to understand for learners who are new to Python.

Here’s an example:

names = ['Alice', 'Bob', 'Charlie']
lengths = []
for name in names:
    lengths.append(len(name))

Output:

[5, 3, 7]

In the snippet above, we create a new empty list called lengths. We then loop through each name in the names list and append the length of each name to the lengths list using the len() function.

Method 2: Using List Comprehension

List comprehension provides a more concise way to create lists based on existing lists. This method is both efficient and Pythonic, allowing developers to accomplish the same task as a for loop in just one line of code.

Here’s an example:

names = ['Alice', 'Bob', 'Charlie']
lengths = [len(name) for name in names]

Output:

[5, 3, 7]

The previous list is regenerated using list comprehension. We define lengths with a single expression that iterates over names and applies the len() function to each element.

Method 3: Using the map function

The map function applies a given function to each item of an iterable and returns a map object with the results. This method can be used to apply the len() function to each element in the string array efficiently.

Here’s an example:

names = ['Alice', 'Bob', 'Charlie']
lengths = list(map(len, names))

Output:

[5, 3, 7]

The map() function is passed the len function and our array of names. This generates a map object which is then converted into a list, producing our desired list of lengths.

Method 4: Using a Lambda Function with map

Lambda functions provide a quick way of creating short, anonymous functions in Python. When combined with map(), they can be very powerful for simple transformations or computations such as calculating string lengths.

Here’s an example:

names = ['Alice', 'Bob', 'Charlie']
lengths = list(map(lambda name: len(name), names))

Output:

[5, 3, 7]

Here, a lambda function that calculates the length of a given input is mapped to each element of the names list. This results in a list of the lengths that correspond to the elements of the initial array.

Bonus One-Liner Method 5: Using the operator module

Python’s operator module provides a set of efficient functions corresponding to the intrinsic operators of Python. For obtaining lengths, the operator.itemgetter function can be utilized with map to achieve our goal.

Here’s an example:

import operator
names = ['Alice', 'Bob', 'Charlie']
lengths = list(map(operator.length_hint, names))

Output:

[5, 3, 7]

We utilize the length_hint() function from the operator module, which serves as a hint to the length of an object. Mapped over our string array, it produces the desired lengths efficiently.

Summary/Discussion

  • Method 1: For Loop. Beginner-friendly. More verbose. Efficient for small datasets but might be less suitable for large datasets due to slower performance.
  • Method 2: List Comprehension. Pythonic and concise. Efficient for both small and large datasets. However, it might be less readable for those new to Python.
  • Method 3: map function. Functional approach. Efficient and clean, but the syntax can be less intuitive for beginners compared to list comprehensions.
  • Method 4: Lambda Function with map. Similar benefits and drawbacks to method 3, with added flexibility due to the use of lambda.
  • Method 5: Using the operator module. Provides a highly optimized way to perform this common operation. May be unfamiliar to some Python developers.