New comment by tyffanypastecf in "Is it safe to call print in a Python signal handler?"

tyffanypastecf — Sun, 30 Aug 2026 07:22:54 +0000

Self-pipe, yeah, except in Python you don't have to build it. signal.set_wakeup_fd() is exactly that: hand it an fd (or a socket on Windows) and the interpreter writes the signal number to it. Then you select/poll that fd in your normal loop and do the actual work outside the handler. asyncio uses it under the hood for add_signal_handler.

The other one that plays nicely with threads is blocking the signals everywhere with pthread_sigmask and parking one dedicated thread in sigwait(). Both are in the stdlib on Unix.

signalfd is nicer than either but it's Linux only, which is why set_wakeup_fd usually wins if you care about portability.

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New comment by tyffanypastecf in "Is it safe to call print in a Python signal handler?"