The NumPy library has a function named quantile() that will quickly calculate the quantiles of a dataset for you.

quantile() takes two parameters. The first is the dataset that you are using. The second parameter is a single number or a list of numbers between 0 and 1. These numbers represent the places in the data where you want to split.

For example, if you only wanted the value that split the first 10% of the data apart from the remaining 90%, you could use this code:

import numpy as np

dataset = [5, 10, -20, 42, -9, 10]
ten_percent = np.quantile(dataset, 0.10)

ten_percent now holds the value -14.5. This result technically isn’t a quantile, because it isn’t splitting the dataset into groups of equal sizes — this value splits the data into one group with 10% of the data and another with 90%.

However, it would still be useful if you were curious about whether a data point was in the bottom 10% of the dataset.