Python Sort List of Strings by Length

π‘ Problem Formulation: When working with lists of strings in Python, you may encounter a scenario where you need to sort the list not by alphabetical order, but by the length of the strings. For instance, given a list `["apple", "fig", "banana"]`, you’d want to reorganize the list to `["fig", "apple", "banana"]`, arranging the words by ascending length.

Method 1: Using sorted() with len()

The built-in `sorted()` function can be used to sort any iterable. When sorting a list of strings by length, you can pass `len` as the `key` argument, which instructs `sorted()` to sort by the length of the strings.

Here’s an example:

```fruits = ["apple", "fig", "banana"]
sorted_fruits = sorted(fruits, key=len)
print(sorted_fruits)
# Output: ["fig", "apple", "banana"]```

In this snippet, `sorted(fruits, key=len)` tells Python to sort the `fruits` list, using the length of each string as the sorting key. The sorted list is `["fig", "apple", "banana"]`, ordered by ascending string length.

Method 2: Using the sort() Method with a Lambda Function

The `sort()` method sorts a list in place. If you want to sort a list by the lengths of its strings, you can use a lambda function as the key, which will be used to determine the strings’ lengths during the sort.

Here’s an example:

```fruits = ["apple", "fig", "banana"]
fruits.sort(key=lambda fruit: len(fruit))
print(fruits)
# Output: ["fig", "apple", "banana"]```

By calling `fruits.sort(key=lambda fruit: len(fruit))`, we sort `fruits` in place, using a lambda function that returns the length of each string as the key. The list is modified to `["fig", "apple", "banana"]`, with shorter strings coming first.

Method 3: Using the sort() Method with len()

Similarly to the sorted function, the `sort()` method can also be used with `len()` to sort the list of strings by their lengths, manipulating the original list rather than creating a copy.

Here’s an example:

```fruits = ["apple", "fig", "banana"]
fruits.sort(key=len)
print(fruits)
# Output: ["fig", "apple", "banana"]```

The expression `fruits.sort(key=len)` sorts the `fruits` list in place, using the length of the strings as the key for sorting. The manipulated list appears as `["fig", "apple", "banana"]`, sorted by ascending length.

Method 4: Using List Comprehension With Tuple Sorting

Python sorts tuples based on the first element by default. You can create a list of tuples, where the first element is the string length, and then sort it. Finally, use list comprehension to extract the sorted strings.

Here’s an example:

```fruits = ["apple", "fig", "banana"]
fruits_with_length = [(len(fruit), fruit) for fruit in fruits]
fruits_with_length.sort()
sorted_fruits = [fruit for _, fruit in fruits_with_length]
print(sorted_fruits)
# Output: ["fig", "apple", "banana"]```

This code first pairs each string with its length in a tuple, sorts the list of tuples, and then strips away the lengths, leaving a list of strings sorted by length: `["fig", "apple", "banana"]`.

Bonus One-Liner Method 5: Using sorted() and a Generator Expression

For a concise one-liner, you can combine `sorted()` with a generator expression, which creates an iterable of tuples with string lengths and strings.

Here’s an example:

```fruits = ["apple", "fig", "banana"]
sorted_fruits = [fruit for _, fruit in sorted((len(fruit), fruit) for fruit in fruits)]
print(sorted_fruits)  # Output: ["fig", "apple", "banana"]```

This one-liner sorts a generator expression that produces tuples of string lengths and strings. The result is a new list of strings sorted by length: `["fig", "apple", "banana"]`.

Summary/Discussion

• Method 1 (`sorted()` with `len()`): Returns a new sorted list; non-destructive.
• Method 2 (`sort()` with Lambda): Sorts the list in place using a lambda function; efficient for long lists.
• Method 3 (`sort()` with `len()`): Sorts the list in place; fewer keystrokes than a lambda function.
• Method 4 (List Comprehension with Tuple Sorting): More complex; helpful when additional sorting conditions are needed.
• Bonus Method 5 (One-Liner with `sorted()` and Generator): Extremely concise; best for those who prefer one-liners.

For immutable sorting, Method 1 is preferred, while Method 2 and 3 provide in-place sorting. Method 4 and the Bonus Method 5 offer a different syntax style but might be less readable for beginners.