Neat. I was going to ask for a source saying that `dict.setdefault` is atomic, but I found it myself: Ticket: https://bugs.python.org/issue13521 https://bugs.p

Neat. I was going to ask for a source saying that `dict.setdefault` is atomic, but I found it myself: Ticket: https://bugs.python.org/issue13521 https://bugs.python.org/issue13521 Patch: https://hg.python.org/cpython/rev/90572ccda12c https://hg.python.org/cpython/rev/90572ccda12c