A Python function to filter a list of values for outliers by using an interquartile filter

outliers_filter.py

import math


def filter_outliers(values: list) -> list:
    array_length = len(values)

    if array_length < 4:
        return values

    values.sort()

    if (array_length % 4) == 0:
        quarter = int(array_length / 4)

        q1 = (1 / 2) * (values[quarter] + values[quarter + 1])
        q3 = (1 / 2) * (values[quarter * 3] + values[(quarter * 3) + 1])
    else:
        q1 = values[math.floor(array_length / 4 + 1)]
        q3 = values[math.ceil(array_length * (3 / 4) + 1)]

    iqr = q3 - q1
    max_value = q3 + iqr * 1.5
    min_value = q1 - iqr * 1.5

    return list(x for x in values if max_value >= x >= min_value)