How to create a line in Shapely using starting point, length, and an angle

user_15636383 0
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I found this code but it requires both first and second point to create a line. How can I change it so it works with only first point, length of the line, and an angle?

from shapely.geometry import LineString
from shapely.geometry import Point

p = Point(5,5)
c = p.buffer(3).boundary
l = LineString([(0,0), (10, 10)])
i = c.intersection(l)

print i.geoms[0].coords[0]
(2.8786796564403576, 2.8786796564403576)

print i.geoms[1].coords[0]
(7.121320343559642, 7.121320343559642)
shapely geometry python
1 Answers

You have several options:

  1. Calculate the coordinates of the second point using basic trigonometry: 
    import math
from shapely.geometry import LineString, Point

start = Point(0, 0)
length = 1
angle = math.pi / 3

end = Point(start.x + length * math.cos(angle),
            start.y + length * math.sin(angle))
line = LineString([start, end])
print(line)
# LINESTRING (0 0, 0.5000000000000001 0.8660254037844386)
    If your angle is not in radians but in degrees, you should convert it first: 
    angle = 60
angle = math.radians(angle)

  1. Make a horizontal line with the given start point and length, and then rotate it by given angle around the first point:

    from shapely.affinity import rotate
from shapely.geometry import LineString, Point

start = Point(0, 0)
length = 1
angle = math.pi / 3

end = Point(start.x + length, start.y)
line = LineString([start, end])
line = rotate(line, angle, origin=start, use_radians=True)
print(line)
# LINESTRING (0 0, 0.5000000000000001 0.8660254037844386)

    Note that by default rotate function expects angles in degrees, so if we want to pass an angle in radians to it, we have to use the use_radians=True as shown above.

    Alternatively, we could also use translate function to get the endpoint:

    from shapely.affinity import translate
end = translate(start, length)
user_78514700
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