# Sort List by Another List in Python

Shivam Arora Oct 10, 2023

Generally, when we sort lists, we do it in ascending or descending order. However, we can sort a list based on the order of another list in Python.

We will learn how to sort a given list based on the values from another list in this article.

## Use the `zip()` and `sorted()` Functions to Sort the List Based on Another List in Python

In this method, we will use the `zip()` function to create a third object by combining the two given lists, the first which has to be sorted and the second on which the sorting depends.

We can then use the `sorted()` function, which extracts the first elements of each pair of the given lists from the sorted and zipped list.

``````A = ["r", "s", "t", "u", "v", "w", "x", "y", "z"]
B = [0, 1, 1, 0, 1, 2, 2, 0, 1]
result_list = [i for _, i in sorted(zip(B, A))]
print(result_list)
``````

Output:

``````['r', 'u', 'y', 's', 't', 'v', 'z', 'w', 'x']
``````

## Use the `NumPy` Module to Sort the List Based on Another List in Python

In this method, we convert the lists into `NumPy` arrays then apply the sorting algorithm to the lists. We sort the array on which the sorting depends using the `argsort()` function and then use those values to filter the second array.

See the following example.

``````import numpy

A = ["r", "s", "t", "u", "v", "w", "x", "y", "z"]
B = [0, 1, 1, 0, 1, 2, 2, 0, 1]

A = numpy.array(A)
B = numpy.array(B)
inds = B.argsort()
sorted_a = A[B]
print(sorted_a)
``````

Output:

``````['r' 's' 's' 'r' 's' 't' 't' 'r' 's']
``````

To get the final data in a list, use the `tolist()` function.

## Use the `more_itertools.sort_together` to Sort the List Based on Another List in Python

The `more_itertools` module is an extension to the `itertools` module. The `sort_together` function returns the input iterables sorted together, with the list in `key_list` argument as the priority for sorting.

For example,

``````from more_itertools import sort_together

X = ["r", "s", "t", "u", "v", "w", "x", "y", "z"]
Y = [0, 1, 1, 0, 1, 2, 2, 0, 1]
s = sort_together([Y, X])
print(list(s))
``````

Output:

``````['r', 'u', 'y', 's', 't', 'v', 'z', 'w', 'x']
``````

We need to use the `list()` function to get the final result as a list.