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bpo-28206: Document signals Handlers, Sigmasks and Signals enums #1939

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bpo-28206: Document signals Handlers, Sigmasks and Signals enums
desbma Jun 4, 2017
7927549
Change wording as suggested by @berkerpeksag
desbma Aug 24, 2018
97a67fd
Add enum usage example
desbma Aug 24, 2018
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23 changes: 19 additions & 4 deletions Doc/library/signal.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -67,10 +67,10 @@ Module contents
signal (SIG*), handler (:const:`SIG_DFL`, :const:`SIG_IGN`) and sigmask
(:const:`SIG_BLOCK`, :const:`SIG_UNBLOCK`, :const:`SIG_SETMASK`)
related constants listed below were turned into
:class:`enums <enum.IntEnum>`.
:class:`enums <enum.IntEnum>` (:class:`Handlers` and :class:`Sigmasks` respectively).
:func:`getsignal`, :func:`pthread_sigmask`, :func:`sigpending` and
:func:`sigwait` functions return human-readable
:class:`enums <enum.IntEnum>`.
:class:`enums <enum.IntEnum>` as :class:`Signals` objects.


The variables defined in the :mod:`signal` module are:
Expand Down Expand Up @@ -478,8 +478,8 @@ The :mod:`signal` module defines the following functions:

.. _signal-example:

Example
-------
Examples
--------

Here is a minimal example program. It uses the :func:`alarm` function to limit
the time spent waiting to open a file; this is useful if the file is for a
Expand All @@ -503,6 +503,21 @@ be sent, and the handler raises an exception. ::

signal.alarm(0) # Disable the alarm

:class:`enums <enum.IntEnum>` types can be used to convert from signal code to string, or the reverse::

@berkerpeksag berkerpeksag Mar 31, 2019

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I think there's no need to duplicate the first example here. We can enhance it instead of adding another one:

import signal, os

def handler(signum, frame):
    signame = signal.Signals(signum).name
    print(f'Signal handler called with signal {signame} ({signum})')
    raise OSError("Couldn't open device!")

# Set the signal handler and a 5-second alarm
signal.signal(signal.SIGALRM, handler)
# An enum member can also be passed as first argument
signal.signal(signal.Signals['SIGALRM'], handler)
signal.alarm(5)

# This open() may hang indefinitely
fd = os.open('/dev/ttyS0', os.O_RDWR)

signal.alarm(0)          # Disable the alarm

@berkerpeksag berkerpeksag Mar 31, 2019

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Also, it would be nice to document enums at the documentation:

The signal module defines three enums:

.. class:: Signals

.. You may be able to use ``.. enum:: Signals`` instead. I don't know if it's supported now.

   Document it here.

   .. versionadded:: 3.5


import signal, os

def handler(signum, frame):
# signum is an integer code, get the signal name using the signal.Signal enum
signame = signal.Signals(signum).name
print(f'Signal handler called with signal {signame} of code {signum}')

# attach a handler for signal.SIGINT
signame = 'SIGINT'
signal.signal(signal.Signals[signame], handler)



Note on SIGPIPE
---------------

Expand Down