I often write code like:

threads = []
for i in range(10):
  thread = threading.Thread(target=fn, args=(i,))
  thread.start()
  threads.append(thread)

for t in threads:
  t.join()

and would really prefer:

threads = [threading.Thread(target=fn, args=(i,)).start() for i in range(10)]

Is there a reason why start doesn't return self here: https://github.com/python/cpython/blob/3.10/Lib/threading.py#L940 ?

An alternative would be to add a start: bool = False param to the Thread constructor such that you can construct it with start=True. I'm not sure why you'd ever want to construct a Thread but not start it, so I wish that could default to true, but clearly it can't due to backwards compatibility.