threading.Thread: Add start=False parameter to start immediately the thread

It's common to create multiple threads, start them, and then join them. Example:

threads = [
    threading.Thread(target=run_a),
    threading.Thread(target=run_b),
]
for thread in threads:
    thread.start()
...
for thread in threads:
    thread.join()

I propose adding a start=False parameter to threading.Thread to start immediately the thread. The example would become:

threads = [
    threading.Thread(target=run_a, start=True),
    threading.Thread(target=run_b, start=True),
]
...
for thread in threads:
    thread.join()

The new parameter would solve the old issue gh-93293 which requests to return self in start(). The issue example:

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

for t in threads:
  t.join()

would become:

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

for t in threads:
  t.join()

Linked PRs

• gh-155335

Comece revisando o construtor de threading.Thread e o comportamento de start() e join(), depois inspecione o trabalho vinculado em gh-155335. Determine a semântica da API e as implicações de compatibilidade de iniciar durante a construção; considera-se concluído quando o uso proposto funcionar corretamente sem alterar o comportamento existente de Thread.