Affinity rotate changes angle in place

version/platform

All from Anaconda main channel

• Shapely 1.6.4
• Geo’s 3.8.0
• Python 3.7 x64
• Windows 10 x64

Expected behavior and actual behavior.

When applying affinity rotate to line string with an angle in degrees, afterwards the variable containing angle has been permanently changed to radians.

If angle is already in radians, and use_radians=True then works as expected

Steps to reproduce the problem.

from shapely import affinity
from shapely.geometry import LineString
L = 1.6
P = 5
tracker_theta = 129.7  # degrees
tracker1 = LineString([(-L/2, 0), (L/2, 0)])
tracker1rot = affinity.rotate(
    tracker1, tracker_theta)
# tracker_theta has been permanently converted to radians
tracker2 = LineString([(P-L/2, 0), (P+L/2, 0)])
tracker2rot = affinity.rotate(
    tracker2, tracker_theta)

# tracker2rot is incorrect because use_radians is false by default, but tracker theta had been converted in place unexpectedly

Operating system

(For example, Mac OS X 10.12.3)

Shapely version and provenance

(For example, 1.6b4 installed from PyPI using pip)

[sgillies]

@mikofski thanks for coming back with the crucial detail. I hadn’t considered the array.

[mikofski]

Ah, it happens when the variable is a numpy array.

try this:

>>> from shapely import affinity
>>> from shapely.geometry import LineString
>>> import numpy as np

>>> L = 1.6
>>> P = 5
>>> tracker_theta = np.array([129.7])  # degrees
>>> tracker1 = LineString([(-L/2, 0), (L/2, 0)])
>>> tracker1rot = affinity.rotate(tracker1, tracker_theta)

>>> tracker_theta
# array([2.26369204])