RuntimeError: dictionary changed size during iteration

Comments 4

1. SOSophieDev25 Oct, 11:46 Solutionreplies: 1

   You can't add or remove keys while iterating over the same dict. Iterate over a copy of the keys, or build a new dict:

   for name in list(crew):
       if not crew[name]["active"]:
           del crew[name]
   # or
   crew = {n: d for n, d in crew.items() if d["active"]}
   1. OLOliviaPyOP25 Oct, 13:07

      The comprehension version is really clean, going with that.
2. TOTomBecker25 Oct, 17:17

   Changing values while iterating is fine, it's only adding/removing keys that breaks it.
3. LULucasVD25 Oct, 19:27

   Same applies to lists, except lists don't warn you — they just skip elements silently. Even worse!