[Python-Dev] List mutation in list_repr? (original) (raw)

Hrvoje Niksic hrvoje.niksic at avl.com
Tue Dec 6 11:29:07 EST 2016

and I also don’t see any clue in the source as to when [list mutation] would actually happen. Since inside the loop, the list object v is never accessed other than passing v->ob_item[i] to the recursive repr call, there shouldn’t be any mutation on the list object itself.

The individual object can have a reference to the list and (in extreme cases) do with it what it pleases:

class Evil: def init(self, l): self.l = l

 def __repr__(self):
     del l[:]
     return "evil"

l = [] l.append(Evil(l)) l.append(Evil(l)) print(l)

That is not something normal Python code does, but it shouldn't be allowed to crash the interpreter, either.

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