CODEWITHSUNDEEP
pythonpygame
Pietro Grushenko
Pietro Grushenko

Reputation: 53

Pygame: assignment unpacking throws SystemError

I am facing a curious behaviour: assignment unpacking on a 2D vector works perfectly fine, until I subclass it.

$ ipython
Python 3.6.7 (default, Oct 22 2018, 11:32:17) 
IPython 5.5.0 

pygame 1.9.4
Hello from the pygame community. https://www.pygame.org/contribute.html
In [1]: from pygame.math import Vector2

In [2]: a = Vector2(1,1)

In [3]: x,y = a

In [4]: class myvec(Vector2):
   ...:     pass
   ...: 

In [5]: b = myvec(1,1)

In [6]: z,w = b
---------------------------------------------------------------------------
SystemError                               Traceback (most recent call last)
<ipython-input-6-dc661fdbb625> in <module>()
----> 1 z,w = b

SystemError: src/math.c:2954: bad argument to internal function

Can someone help me figure out what is happening here? Is it a pygame bug that I need to report somewhere else, or am I doing something wrong?

Fun fact: it worked perfectly fine for a while, then it suddenly started throwing this exception and there is no going back.

Upvotes: 4

Views: 58

Answers (1)

vencaslac
vencaslac

Reputation: 2854

This may not be an answer but I made some checks starting from your example. For instance it does on the surface look like your two classes are at least a little different:

 >>> [print(item) for item in dir(a) if item not in dir(b)]
 []
 >>> [print(item) for item in dir(b) if item not in dir(a)]
 __dict__
 __module__
 __weakref__
 [None, None, None]

so it looks like inheritance does add something even though you're, on the surface, just making a copy of the old class.

So let's look at what the original class looks like from here:

Welp, it's implemented in C. but the error does seem to point to line 2954:

    double *other_coords;

That has me stumped, but I would file this as an issue on the github or wait for the issue fix mentioned in the comment to be rolled out

Upvotes: 1

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