Shapely - Resize LineString

resize_line.py

import math
from shapely.geometry import LineString


def get_angle(line: LineString) -> float:
    'Returns the angle (in radians) of a given line in relation with the X axis.'
    start, end = line.boundary
    if end.y - start.y == 0:  # Avoids dividing by zero.
        return math.acos(0)
    return -math.atan((end.x - start.x) / (end.y - start.y))


def resize_line(line: LineString, length: float) -> LineString:
    'Returns a new line with the same center and angle of a given line, but with different length.'
    angle = get_angle(line)
    ext_x = round(length / 2 * math.sin(angle), 6)
    ext_y = round(length / 2 * math.cos(angle), 6)
    return LineString(([line.centroid.x + ext_x, line.centroid.y - ext_y],
                       [line.centroid.x - ext_x, line.centroid.y + ext_y]))