RuntimeError: dictionary changed size during iteration

[antoniosarosi]

Al crear un WeightingFunction que sea symmetrical con claves duplicadas, intenta borrar claves del mapa mientras itera sobre keys():

for (u, v) in self._map.keys():
    if (v, u) in self._map:
        # ...
        if v != u: del self._map[v, u]

Ejemplo:

wf = WeightingFunction({('A', 'B'): 1, ('B', 'A'): 1, ('C', 'D'): 2}, symmetrical=True)
# RuntimeError: dictionary changed size during iteration