5 Best Ways to Sort Tuples by Total Digits in Python

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πŸ’‘ Problem Formulation: In Python, sorting tuples by the total number of digits can be a common task when dealing with data that includes numerical entries. The goal is to rank the tuples based on the cumulative count of digits across all numbers within the tuple. For example, given the list of tuples [ (3, 1), (30, 123), (9, 12), (2, 4) ], the sorted output based on total digits should be [ (3, 1), (2, 4), (9, 12), (30, 123) ].

Method 1: Custom Sort Function

This method utilizes a custom sort function within the sorted() function to calculate the total number of digits for each tuple. It iterates over each element in the tuple, converts it to a string, and counts the length. This count is then used to sort the list of tuples.

Here’s an example:

tuples_list = [(3, 1), (30, 123), (9, 12), (2, 4)]
sorted_tuples = sorted(tuples_list, key=lambda t: sum(len(str(num)) for num in t))
print(sorted_tuples)

Output:

[(3, 1), (2, 4), (9, 12), (30, 123)]

This code snippet defines a list of tuples named tuples_list. Then, it uses the sorted() function with a lambda function as the key. The lambda function computes the total number of digits in each tuple as the sort key. The list is sorted according to these calculated keys.

Method 2: Using the `itemgetter` Function

The operator module in Python provides a function itemgetter which can be used to customize sorting. However, since we are sorting by a custom definition (the sum of digits), we must combine itemgetter with a lambda function to achieve our goal.

Here’s an example:

from operator import itemgetter

tuples_list = [(3, 1), (30, 123), (9, 12), (2, 4)]
mapped_tuples = map(lambda t: sum(len(str(num)) for num in t), tuples_list)
sorted_tuples = sorted(tuples_list, key=itemgetter(*mapped_tuples))
print(sorted_tuples)

Output:

TypeError: argument to itemgetter must be an int or sequence of ints

In this example, the attempt to use itemgetter with a lambda function fails because itemgetter expects integer indices and not a list of computed values. Thus, using itemgetter in this context is not a proper method, and we need to rely on customized sort keys with functions such as lambda.

Method 3: Using NumPy Array

When working with numerical data, NumPy can be a powerful ally for complex operations. By converting our tuples into a NumPy array, we can apply vectorized operations and then argsort, which can improve performance for large datasets.

Here’s an example:

import numpy as np

tuples_list = [(3, 1), (30, 123), (9, 12), (2, 4)]
digits_sum = np.array([sum(len(str(num)) for num in tup) for tup in tuples_list])
sorted_indices = np.argsort(digits_sum)
sorted_tuples = np.array(tuples_list)[sorted_indices]
print(sorted_tuples.tolist())

Output:

[[3, 1], [2, 4], [9, 12], [30, 123]]

The code creates a NumPy array digits_sum that holds the total count of digits for each tuple. It then uses argsort to get the sorted indices based on this count. Finally, it reindexes the original list of tuples using these sorted indices to get the sorted list sorted_tuples and converts it back to a Python list for display.

Method 4: In-Place Sort with `sort` Method

The sort method is a list method that sorts the list in place. It’s efficient when you want to alter the original list and also supports a custom sort key. The in-place sorting can save memory when handling large data.

Here’s an example:

tuples_list = [(3, 1), (30, 123), (9, 12), (2, 4)]
tuples_list.sort(key=lambda t: sum(len(str(num)) for num in t))
print(tuples_list)

Output:

[(3, 1), (2, 4), (9, 12), (30, 123)]

This example directly sorts tuples_list in place using the sort method and a lambda function as the key. The sorted list overwrites the original list in memory.

Bonus One-Liner Method 5: List Comprehension and Sorted

A one-liner variant using list comprehension and the sorted() function can be succinct and clear for those familiar with Python’s syntactic sugar. This method is great for writing concise code.

Here’s an example:

tuples_list = [(3, 1), (30, 123), (9, 12), (2, 4)]
sorted_tuples = sorted(tuples_list, key=lambda t: sum(len(str(num)) for num in t))
print(sorted_tuples)

Output:

[(3, 1), (2, 4), (9, 12), (30, 123)]

The one-liner example puts the lambda function directly inside the sorted call. It exhibits the same behavior as Method 1, providing a sorted list based on the total digit count in a concise manner.

Summary/Discussion

  • Method 1: Custom Sort Function. Flexible approach for any sort condition. It requires defining a custom key function, which can be less efficient for large datasets. Ideal for typical use-cases.
  • Method 2: Using the `itemgetter` Function. This approach is not suited for the given problem since `itemgetter` is designed for different use-cases, usually for fetching items by index.
  • Method 3: Using NumPy Array. It is efficient and powerful especially for numeric operations and large datasets. However, it adds a dependency to the NumPy library, which may not be ideal for all environments.
  • Method 4: In-Place Sort with `sort` Method. It alters the original list and is memory efficient. This might be undesirable if maintaining the original order or the data is important.
  • Bonus One-Liner Method 5: List Comprehension and Sorted. Offers clean, readable syntax in a single line. This is effective for small datasets or scripts where brevity is valued over explicitness.