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

Rate this post

π‘ 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

Pythonβ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.