import math


def cal_line_length(point1, point2):
    """Calculate the length of line.

    Args:
        point1 (List): [x,y]
        point2 (List): [x,y]
    Returns:
        length (float)
    """
    return math.sqrt(
        math.pow(point1[0] - point2[0], 2) +
        math.pow(point1[1] - point2[1], 2))