Pymunk: Issue with Removing Constraints from Body about pymunk

[viblo]

Good question!
So, when you create a constraint you assign it to two bodies, like j = pymunk.PinJoint(body1, body2). At this point the constraint object will keep a reference to the bodies (this is not exposed in the API). For convenience its also possible to get the constraint(s) out from the body, with body.constraints as you write. If the constraint is not needed anymore and all references to it are deleted, then the reference between the constraint and body will also be cleaned up eventually (behind the scenes its implemented as a weakset, so this cleanup depends on the garbage collector).

>>> import pymunk
>>> b1 = pymunk.Body()
>>> b2 = pymunk.Body()
>>> j = pymunk.PinJoint(b1, b2)
>>> b1.constraints
{<pymunk.constraints.PinJoint object at 0x0000019DAC940F50>}
>>> del j
... some other code that triggers garbage collection
>>> b1.constraints
set()

Note that the space is not involved here. The constraint - body reference can exist outside the space. (but of course, the constraint wont be cleaned up while the constraint and body are in the space since the space will keep a reference to the constraint)

[BenjaminKerbal]

Hello,

Thank you for the detailed explanation. This clarifies how constraints are managed in Pymunk, and why the constraints remain in body.constraints even though they have been removed from the space. I will take your advice and ensure all references to constraints are removed when they are no longer needed.

[viblo]

Great! I made a small improvement to the docs as well.