cpython/Doc/library/signal.rst

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:mod:`signal` --- Set handlers for asynchronous events
======================================================
.. module:: signal
:synopsis: Set handlers for asynchronous events.
--------------
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This module provides mechanisms to use signal handlers in Python.
General rules
-------------
The :func:`signal.signal` function allows defining custom handlers to be
executed when a signal is received. A small number of default handlers are
installed: :const:`SIGPIPE` is ignored (so write errors on pipes and sockets
can be reported as ordinary Python exceptions) and :const:`SIGINT` is
translated into a :exc:`KeyboardInterrupt` exception.
A handler for a particular signal, once set, remains installed until it is
explicitly reset (Python emulates the BSD style interface regardless of the
underlying implementation), with the exception of the handler for
:const:`SIGCHLD`, which follows the underlying implementation.
Execution of Python signal handlers
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
A Python signal handler does not get executed inside the low-level (C) signal
handler. Instead, the low-level signal handler sets a flag which tells the
:term:`virtual machine` to execute the corresponding Python signal handler
at a later point(for example at the next :term:`bytecode` instruction).
This has consequences:
* It makes little sense to catch synchronous errors like :const:`SIGFPE` or
:const:`SIGSEGV` that are caused by an invalid operation in C code. Python
will return from the signal handler to the C code, which is likely to raise
the same signal again, causing Python to apparently hang. From Python 3.3
onwards, you can use the :mod:`faulthandler` module to report on synchronous
errors.
* A long-running calculation implemented purely in C (such as regular
expression matching on a large body of text) may run uninterrupted for an
arbitrary amount of time, regardless of any signals received. The Python
signal handlers will be called when the calculation finishes.
.. _signals-and-threads:
Signals and threads
^^^^^^^^^^^^^^^^^^^
Python signal handlers are always executed in the main Python thread,
even if the signal was received in another thread. This means that signals
can't be used as a means of inter-thread communication. You can use
the synchronization primitives from the :mod:`threading` module instead.
Besides, only the main thread is allowed to set a new signal handler.
Module contents
---------------
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.. versionchanged:: 3.5
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>`.
:func:`getsignal`, :func:`pthread_sigmask`, :func:`sigpending` and
:func:`sigwait` functions return human-readable
:class:`enums <enum.IntEnum>`.
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The variables defined in the :mod:`signal` module are:
.. data:: SIG_DFL
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This is one of two standard signal handling options; it will simply perform
the default function for the signal. For example, on most systems the
default action for :const:`SIGQUIT` is to dump core and exit, while the
default action for :const:`SIGCHLD` is to simply ignore it.
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.. data:: SIG_IGN
This is another standard signal handler, which will simply ignore the given
signal.
.. data:: SIG*
All the signal numbers are defined symbolically. For example, the hangup signal
is defined as :const:`signal.SIGHUP`; the variable names are identical to the
names used in C programs, as found in ``<signal.h>``. The Unix man page for
':c:func:`signal`' lists the existing signals (on some systems this is
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:manpage:`signal(2)`, on others the list is in :manpage:`signal(7)`). Note that
not all systems define the same set of signal names; only those names defined by
the system are defined by this module.
.. data:: CTRL_C_EVENT
The signal corresponding to the :kbd:`Ctrl+C` keystroke event. This signal can
only be used with :func:`os.kill`.
Availability: Windows.
.. versionadded:: 3.2
.. data:: CTRL_BREAK_EVENT
The signal corresponding to the :kbd:`Ctrl+Break` keystroke event. This signal can
only be used with :func:`os.kill`.
Availability: Windows.
.. versionadded:: 3.2
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.. data:: NSIG
One more than the number of the highest signal number.
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.. data:: ITIMER_REAL
Decrements interval timer in real time, and delivers :const:`SIGALRM` upon
expiration.
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.. data:: ITIMER_VIRTUAL
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Decrements interval timer only when the process is executing, and delivers
SIGVTALRM upon expiration.
.. data:: ITIMER_PROF
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Decrements interval timer both when the process executes and when the
system is executing on behalf of the process. Coupled with ITIMER_VIRTUAL,
this timer is usually used to profile the time spent by the application
in user and kernel space. SIGPROF is delivered upon expiration.
.. data:: SIG_BLOCK
A possible value for the *how* parameter to :func:`pthread_sigmask`
indicating that signals are to be blocked.
.. versionadded:: 3.3
.. data:: SIG_UNBLOCK
A possible value for the *how* parameter to :func:`pthread_sigmask`
indicating that signals are to be unblocked.
.. versionadded:: 3.3
.. data:: SIG_SETMASK
A possible value for the *how* parameter to :func:`pthread_sigmask`
indicating that the signal mask is to be replaced.
.. versionadded:: 3.3
The :mod:`signal` module defines one exception:
.. exception:: ItimerError
Raised to signal an error from the underlying :func:`setitimer` or
:func:`getitimer` implementation. Expect this error if an invalid
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interval timer or a negative time is passed to :func:`setitimer`.
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This error is a subtype of :exc:`OSError`.
.. versionadded:: 3.3
This error used to be a subtype of :exc:`IOError`, which is now an
alias of :exc:`OSError`.
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The :mod:`signal` module defines the following functions:
.. function:: alarm(time)
If *time* is non-zero, this function requests that a :const:`SIGALRM` signal be
sent to the process in *time* seconds. Any previously scheduled alarm is
canceled (only one alarm can be scheduled at any time). The returned value is
then the number of seconds before any previously set alarm was to have been
delivered. If *time* is zero, no alarm is scheduled, and any scheduled alarm is
canceled. If the return value is zero, no alarm is currently scheduled. (See
the Unix man page :manpage:`alarm(2)`.) Availability: Unix.
.. function:: getsignal(signalnum)
Return the current signal handler for the signal *signalnum*. The returned value
may be a callable Python object, or one of the special values
:const:`signal.SIG_IGN`, :const:`signal.SIG_DFL` or :const:`None`. Here,
:const:`signal.SIG_IGN` means that the signal was previously ignored,
:const:`signal.SIG_DFL` means that the default way of handling the signal was
previously in use, and ``None`` means that the previous signal handler was not
installed from Python.
.. function:: strsignal(signalnum)
Return the system description of the signal *signalnum*, such as
"Interrupt", "Segmentation fault", etc. Returns :const:`None` if the signal
is not recognized.
.. versionadded:: 3.8
.. function:: valid_signals()
Return the set of valid signal numbers on this platform. This can be
less than ``range(1, NSIG)`` if some signals are reserved by the system
for internal use.
.. versionadded:: 3.8
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.. function:: pause()
Cause the process to sleep until a signal is received; the appropriate handler
will then be called. Returns nothing. Not on Windows. (See the Unix man page
:manpage:`signal(2)`.)
See also :func:`sigwait`, :func:`sigwaitinfo`, :func:`sigtimedwait` and
:func:`sigpending`.
.. function:: pthread_kill(thread_id, signalnum)
Send the signal *signalnum* to the thread *thread_id*, another thread in the
same process as the caller. The target thread can be executing any code
(Python or not). However, if the target thread is executing the Python
interpreter, the Python signal handlers will be :ref:`executed by the main
thread <signals-and-threads>`. Therefore, the only point of sending a
signal to a particular Python thread would be to force a running system call
to fail with :exc:`InterruptedError`.
Use :func:`threading.get_ident()` or the :attr:`~threading.Thread.ident`
attribute of :class:`threading.Thread` objects to get a suitable value
for *thread_id*.
If *signalnum* is 0, then no signal is sent, but error checking is still
performed; this can be used to check if the target thread is still running.
Availability: Unix (see the man page :manpage:`pthread_kill(3)` for further
information).
See also :func:`os.kill`.
.. versionadded:: 3.3
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.. function:: pthread_sigmask(how, mask)
Fetch and/or change the signal mask of the calling thread. The signal mask
is the set of signals whose delivery is currently blocked for the caller.
Return the old signal mask as a set of signals.
The behavior of the call is dependent on the value of *how*, as follows.
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* :data:`SIG_BLOCK`: The set of blocked signals is the union of the current
set and the *mask* argument.
* :data:`SIG_UNBLOCK`: The signals in *mask* are removed from the current
set of blocked signals. It is permissible to attempt to unblock a
signal which is not blocked.
* :data:`SIG_SETMASK`: The set of blocked signals is set to the *mask*
argument.
*mask* is a set of signal numbers (e.g. {:const:`signal.SIGINT`,
:const:`signal.SIGTERM`}). Use :func:`~signal.valid_signals` for a full
mask including all signals.
For example, ``signal.pthread_sigmask(signal.SIG_BLOCK, [])`` reads the
signal mask of the calling thread.
Availability: Unix. See the man page :manpage:`sigprocmask(3)` and
:manpage:`pthread_sigmask(3)` for further information.
See also :func:`pause`, :func:`sigpending` and :func:`sigwait`.
.. versionadded:: 3.3
.. function:: setitimer(which, seconds, interval=0.0)
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Sets given interval timer (one of :const:`signal.ITIMER_REAL`,
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:const:`signal.ITIMER_VIRTUAL` or :const:`signal.ITIMER_PROF`) specified
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by *which* to fire after *seconds* (float is accepted, different from
:func:`alarm`) and after that every *interval* seconds (if *interval*
is non-zero). The interval timer specified by *which* can be cleared by
setting *seconds* to zero.
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When an interval timer fires, a signal is sent to the process.
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The signal sent is dependent on the timer being used;
:const:`signal.ITIMER_REAL` will deliver :const:`SIGALRM`,
Merged revisions 61440-61441,61443,61445-61448,61451-61452,61455-61457,61459-61464,61466-61467,61469-61470,61476-61477,61479,61481-61482,61485,61487,61490,61493-61494,61497,61499-61502,61505-61506,61508,61511-61514,61519,61521-61522,61530-61531,61533-61537,61541-61555,61557-61558,61561-61562,61566-61569,61572-61574,61578-61579,61583-61584,61588-61589,61592,61594,61598-61601,61603-61604,61607-61612,61617,61619-61620,61624,61626,61628-61630,61635-61638,61640-61643,61645,61648,61653-61655,61659-61662,61664,61666,61668-61671,61673,61675,61679-61680,61682,61685-61686,61689-61695,61697-61699,61701-61703,61706,61710,61713,61717,61723,61726-61730,61736,61738,61740,61742,61745-61752,61754-61760,61762-61764,61768,61770-61772,61774-61775,61784-61787,61789-61792,61794-61795,61797-61806,61808-61809,61811-61812,61814-61819,61824,61826-61833,61835-61840,61843-61845,61848,61850,61854-61862,61865-61866,61868,61872-61873,61876-61877,61883-61888,61890-61891,61893-61899,61901-61903,61905-61912,61914,61917,61920-61921,61927,61930,61932-61934,61939,61941-61942,61944-61951,61955,61960-61963,61980,61982-61983,61991,61994-61996,62001-62003,62008-62010,62016-62017,62022,62024,62027,62031-62034,62041,62045-62046,62055-62058,62060-62066,62068-62074,62076-62079,62081-62083,62086-62089,62092-62094,62098,62101,62104,62106-62109,62115-62122,62124-62125,62127-62128,62130,62132,62134-62137,62139-62142,62144,62146-62148,62150-62152,62155-62161 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r62127 | trent.nelson | 2008-04-03 08:39:17 -0700 (Thu, 03 Apr 2008) | 1 line Remove the building of Berkeley DB step; _bsddb44.vcproj takes care of this for us now. ........ r62136 | amaury.forgeotdarc | 2008-04-03 16:07:55 -0700 (Thu, 03 Apr 2008) | 9 lines #1733757: the interpreter would hang on shutdown, if the function set by sys.settrace calls threading.currentThread. The correction somewhat improves the code, but it was close. Many thanks to the "with" construct, which turns python code into C calls. I wonder if it is not better to sys.settrace(None) just after running the __main__ module and before finalization. ........ r62141 | jeffrey.yasskin | 2008-04-03 21:51:19 -0700 (Thu, 03 Apr 2008) | 5 lines Doh! os.read() raises an OSError, not an IOError when it's interrupted. And fix some flakiness in test_itimer_prof, which could detect that the timer had reached 0 before the signal arrived announcing that fact. ........ r62142 | fred.drake | 2008-04-03 22:41:30 -0700 (Thu, 03 Apr 2008) | 4 lines - Issue #2385: distutils.core.run_script() makes __file__ available, so the controlled environment will more closely mirror the typical script environment. This supports setup.py scripts that refer to data files. ........ r62147 | fred.drake | 2008-04-04 04:31:14 -0700 (Fri, 04 Apr 2008) | 6 lines my previous change did what I said it should not: it changed the current directory to the directory in which the setup.py script lived (which made __file__ wrong) fixed, with test that the script is run in the current directory of the caller ........ r62148 | fred.drake | 2008-04-04 04:38:51 -0700 (Fri, 04 Apr 2008) | 2 lines stupid, stupid, stupid! ........ r62150 | jeffrey.yasskin | 2008-04-04 09:48:19 -0700 (Fri, 04 Apr 2008) | 2 lines Oops again. EINTR is in errno, not signal. ........ r62158 | andrew.kuchling | 2008-04-04 19:42:20 -0700 (Fri, 04 Apr 2008) | 1 line Minor edits ........ r62159 | andrew.kuchling | 2008-04-04 19:47:07 -0700 (Fri, 04 Apr 2008) | 1 line Markup fix; explain what interval timers do; typo fix ........ r62160 | andrew.kuchling | 2008-04-04 20:38:39 -0700 (Fri, 04 Apr 2008) | 1 line Various edits ........ r62161 | neal.norwitz | 2008-04-04 21:26:31 -0700 (Fri, 04 Apr 2008) | 9 lines Prevent test_sqlite from hanging on older versions of sqlite. The problem is that when trying to do the second insert, sqlite seems to sleep for a very long time. Here is the output from strace: read(6, "SQLite format 3\0\4\0\1\1\0@ \0\0\0\1\0\0\0\0"..., 1024) = 1024 nanosleep({4294, 966296000}, <unfinished ...> I don't know which version this was fixed in, but 3.2.1 definitely fails. ........
2008-04-05 01:47:45 -03:00
:const:`signal.ITIMER_VIRTUAL` sends :const:`SIGVTALRM`,
and :const:`signal.ITIMER_PROF` will deliver :const:`SIGPROF`.
The old values are returned as a tuple: (delay, interval).
Merged revisions 75365,75394,75402-75403,75418,75459,75484,75592-75596,75600,75602-75607,75610-75613,75616-75617,75623,75627,75640,75647,75696,75795 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r75365 | georg.brandl | 2009-10-11 22:16:16 +0200 (So, 11 Okt 2009) | 1 line Fix broken links found by "make linkcheck". scipy.org seems to be done right now, so I could not verify links going there. ........ r75394 | georg.brandl | 2009-10-13 20:10:59 +0200 (Di, 13 Okt 2009) | 1 line Fix markup. ........ r75402 | georg.brandl | 2009-10-14 17:51:48 +0200 (Mi, 14 Okt 2009) | 1 line #7125: fix typo. ........ r75403 | georg.brandl | 2009-10-14 17:57:46 +0200 (Mi, 14 Okt 2009) | 1 line #7126: os.environ changes *do* take effect in subprocesses started with os.system(). ........ r75418 | georg.brandl | 2009-10-14 20:48:32 +0200 (Mi, 14 Okt 2009) | 1 line #7116: str.join() takes an iterable. ........ r75459 | georg.brandl | 2009-10-17 10:57:43 +0200 (Sa, 17 Okt 2009) | 1 line Fix refleaks in _ctypes PyCSimpleType_New, which fixes the refleak seen in test___all__. ........ r75484 | georg.brandl | 2009-10-18 09:58:12 +0200 (So, 18 Okt 2009) | 1 line Fix missing word. ........ r75592 | georg.brandl | 2009-10-22 09:05:48 +0200 (Do, 22 Okt 2009) | 1 line Fix punctuation. ........ r75593 | georg.brandl | 2009-10-22 09:06:49 +0200 (Do, 22 Okt 2009) | 1 line Revert unintended change. ........ r75594 | georg.brandl | 2009-10-22 09:56:02 +0200 (Do, 22 Okt 2009) | 1 line Fix markup. ........ r75595 | georg.brandl | 2009-10-22 09:56:56 +0200 (Do, 22 Okt 2009) | 1 line Fix duplicate target. ........ r75596 | georg.brandl | 2009-10-22 10:05:04 +0200 (Do, 22 Okt 2009) | 1 line Add a new directive marking up implementation details and start using it. ........ r75600 | georg.brandl | 2009-10-22 13:01:46 +0200 (Do, 22 Okt 2009) | 1 line Make it more robust. ........ r75602 | georg.brandl | 2009-10-22 13:28:06 +0200 (Do, 22 Okt 2009) | 1 line Document new directive. ........ r75603 | georg.brandl | 2009-10-22 13:28:23 +0200 (Do, 22 Okt 2009) | 1 line Allow short form with text as argument. ........ r75604 | georg.brandl | 2009-10-22 13:36:50 +0200 (Do, 22 Okt 2009) | 1 line Fix stylesheet for multi-paragraph impl-details. ........ r75605 | georg.brandl | 2009-10-22 13:48:10 +0200 (Do, 22 Okt 2009) | 1 line Use "impl-detail" directive where applicable. ........ r75606 | georg.brandl | 2009-10-22 17:00:06 +0200 (Do, 22 Okt 2009) | 1 line #6324: membership test tries iteration via __iter__. ........ r75607 | georg.brandl | 2009-10-22 17:04:09 +0200 (Do, 22 Okt 2009) | 1 line #7088: document new functions in signal as Unix-only. ........ r75610 | georg.brandl | 2009-10-22 17:27:24 +0200 (Do, 22 Okt 2009) | 1 line Reorder __slots__ fine print and add a clarification. ........ r75611 | georg.brandl | 2009-10-22 17:42:32 +0200 (Do, 22 Okt 2009) | 1 line #7035: improve docs of the various <method>_errors() functions, and give them docstrings. ........ r75612 | georg.brandl | 2009-10-22 17:52:15 +0200 (Do, 22 Okt 2009) | 1 line #7156: document curses as Unix-only. ........ r75613 | georg.brandl | 2009-10-22 17:54:35 +0200 (Do, 22 Okt 2009) | 1 line #6977: getopt does not support optional option arguments. ........ r75616 | georg.brandl | 2009-10-22 18:17:05 +0200 (Do, 22 Okt 2009) | 1 line Add proper references. ........ r75617 | georg.brandl | 2009-10-22 18:20:55 +0200 (Do, 22 Okt 2009) | 1 line Make printout margin important. ........ r75623 | georg.brandl | 2009-10-23 10:14:44 +0200 (Fr, 23 Okt 2009) | 1 line #7188: fix optionxform() docs. ........ r75627 | fred.drake | 2009-10-23 15:04:51 +0200 (Fr, 23 Okt 2009) | 2 lines add further note about what's passed to optionxform ........ r75640 | neil.schemenauer | 2009-10-23 21:58:17 +0200 (Fr, 23 Okt 2009) | 2 lines Improve some docstrings in the 'warnings' module. ........ r75647 | georg.brandl | 2009-10-24 12:04:19 +0200 (Sa, 24 Okt 2009) | 1 line Fix markup. ........ r75696 | georg.brandl | 2009-10-25 21:25:43 +0100 (So, 25 Okt 2009) | 1 line Fix a demo. ........ r75795 | georg.brandl | 2009-10-27 16:10:22 +0100 (Di, 27 Okt 2009) | 1 line Fix a strange mis-edit. ........
2009-10-27 12:28:25 -03:00
Attempting to pass an invalid interval timer will cause an
:exc:`ItimerError`. Availability: Unix.
.. function:: getitimer(which)
Merged revisions 61440-61441,61443,61445-61448,61451-61452,61455-61457,61459-61464,61466-61467,61469-61470,61476-61477,61479,61481-61482,61485,61487,61490,61493-61494,61497,61499-61502,61505-61506,61508,61511-61514,61519,61521-61522,61530-61531,61533-61537,61541-61555,61557-61558,61561-61562,61566-61569,61572-61574,61578-61579,61583-61584,61588-61589,61592,61594,61598-61601,61603-61604,61607-61612,61617,61619-61620,61624,61626,61628-61630,61635-61638,61640-61643,61645,61648,61653-61655,61659-61662,61664,61666,61668-61671,61673,61675,61679-61680,61682,61685-61686,61689-61695,61697-61699,61701-61703,61706,61710,61713,61717,61723,61726-61730,61736,61738,61740,61742,61745-61752,61754-61760,61762-61764,61768,61770-61772,61774-61775,61784-61787,61789-61792,61794-61795,61797-61806,61808-61809,61811-61812,61814-61819,61824,61826-61833,61835-61840,61843-61845,61848,61850,61854-61862,61865-61866,61868,61872-61873,61876-61877,61883-61888,61890-61891,61893-61899,61901-61903,61905-61912,61914,61917,61920-61921,61927,61930,61932-61934,61939,61941-61942,61944-61951,61955,61960-61963,61980,61982-61983,61991,61994-61996,62001-62003,62008-62010,62016-62017,62022,62024,62027,62031-62034,62041,62045-62046,62055-62058,62060-62066,62068-62074,62076-62079,62081-62083,62086-62089,62092-62094,62098,62101,62104,62106-62109,62115-62122,62124-62125,62127-62128,62130,62132,62134-62137,62139-62142,62144,62146-62148,62150-62152,62155-62161 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r62127 | trent.nelson | 2008-04-03 08:39:17 -0700 (Thu, 03 Apr 2008) | 1 line Remove the building of Berkeley DB step; _bsddb44.vcproj takes care of this for us now. ........ r62136 | amaury.forgeotdarc | 2008-04-03 16:07:55 -0700 (Thu, 03 Apr 2008) | 9 lines #1733757: the interpreter would hang on shutdown, if the function set by sys.settrace calls threading.currentThread. The correction somewhat improves the code, but it was close. Many thanks to the "with" construct, which turns python code into C calls. I wonder if it is not better to sys.settrace(None) just after running the __main__ module and before finalization. ........ r62141 | jeffrey.yasskin | 2008-04-03 21:51:19 -0700 (Thu, 03 Apr 2008) | 5 lines Doh! os.read() raises an OSError, not an IOError when it's interrupted. And fix some flakiness in test_itimer_prof, which could detect that the timer had reached 0 before the signal arrived announcing that fact. ........ r62142 | fred.drake | 2008-04-03 22:41:30 -0700 (Thu, 03 Apr 2008) | 4 lines - Issue #2385: distutils.core.run_script() makes __file__ available, so the controlled environment will more closely mirror the typical script environment. This supports setup.py scripts that refer to data files. ........ r62147 | fred.drake | 2008-04-04 04:31:14 -0700 (Fri, 04 Apr 2008) | 6 lines my previous change did what I said it should not: it changed the current directory to the directory in which the setup.py script lived (which made __file__ wrong) fixed, with test that the script is run in the current directory of the caller ........ r62148 | fred.drake | 2008-04-04 04:38:51 -0700 (Fri, 04 Apr 2008) | 2 lines stupid, stupid, stupid! ........ r62150 | jeffrey.yasskin | 2008-04-04 09:48:19 -0700 (Fri, 04 Apr 2008) | 2 lines Oops again. EINTR is in errno, not signal. ........ r62158 | andrew.kuchling | 2008-04-04 19:42:20 -0700 (Fri, 04 Apr 2008) | 1 line Minor edits ........ r62159 | andrew.kuchling | 2008-04-04 19:47:07 -0700 (Fri, 04 Apr 2008) | 1 line Markup fix; explain what interval timers do; typo fix ........ r62160 | andrew.kuchling | 2008-04-04 20:38:39 -0700 (Fri, 04 Apr 2008) | 1 line Various edits ........ r62161 | neal.norwitz | 2008-04-04 21:26:31 -0700 (Fri, 04 Apr 2008) | 9 lines Prevent test_sqlite from hanging on older versions of sqlite. The problem is that when trying to do the second insert, sqlite seems to sleep for a very long time. Here is the output from strace: read(6, "SQLite format 3\0\4\0\1\1\0@ \0\0\0\1\0\0\0\0"..., 1024) = 1024 nanosleep({4294, 966296000}, <unfinished ...> I don't know which version this was fixed in, but 3.2.1 definitely fails. ........
2008-04-05 01:47:45 -03:00
Returns current value of a given interval timer specified by *which*.
Merged revisions 75365,75394,75402-75403,75418,75459,75484,75592-75596,75600,75602-75607,75610-75613,75616-75617,75623,75627,75640,75647,75696,75795 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r75365 | georg.brandl | 2009-10-11 22:16:16 +0200 (So, 11 Okt 2009) | 1 line Fix broken links found by "make linkcheck". scipy.org seems to be done right now, so I could not verify links going there. ........ r75394 | georg.brandl | 2009-10-13 20:10:59 +0200 (Di, 13 Okt 2009) | 1 line Fix markup. ........ r75402 | georg.brandl | 2009-10-14 17:51:48 +0200 (Mi, 14 Okt 2009) | 1 line #7125: fix typo. ........ r75403 | georg.brandl | 2009-10-14 17:57:46 +0200 (Mi, 14 Okt 2009) | 1 line #7126: os.environ changes *do* take effect in subprocesses started with os.system(). ........ r75418 | georg.brandl | 2009-10-14 20:48:32 +0200 (Mi, 14 Okt 2009) | 1 line #7116: str.join() takes an iterable. ........ r75459 | georg.brandl | 2009-10-17 10:57:43 +0200 (Sa, 17 Okt 2009) | 1 line Fix refleaks in _ctypes PyCSimpleType_New, which fixes the refleak seen in test___all__. ........ r75484 | georg.brandl | 2009-10-18 09:58:12 +0200 (So, 18 Okt 2009) | 1 line Fix missing word. ........ r75592 | georg.brandl | 2009-10-22 09:05:48 +0200 (Do, 22 Okt 2009) | 1 line Fix punctuation. ........ r75593 | georg.brandl | 2009-10-22 09:06:49 +0200 (Do, 22 Okt 2009) | 1 line Revert unintended change. ........ r75594 | georg.brandl | 2009-10-22 09:56:02 +0200 (Do, 22 Okt 2009) | 1 line Fix markup. ........ r75595 | georg.brandl | 2009-10-22 09:56:56 +0200 (Do, 22 Okt 2009) | 1 line Fix duplicate target. ........ r75596 | georg.brandl | 2009-10-22 10:05:04 +0200 (Do, 22 Okt 2009) | 1 line Add a new directive marking up implementation details and start using it. ........ r75600 | georg.brandl | 2009-10-22 13:01:46 +0200 (Do, 22 Okt 2009) | 1 line Make it more robust. ........ r75602 | georg.brandl | 2009-10-22 13:28:06 +0200 (Do, 22 Okt 2009) | 1 line Document new directive. ........ r75603 | georg.brandl | 2009-10-22 13:28:23 +0200 (Do, 22 Okt 2009) | 1 line Allow short form with text as argument. ........ r75604 | georg.brandl | 2009-10-22 13:36:50 +0200 (Do, 22 Okt 2009) | 1 line Fix stylesheet for multi-paragraph impl-details. ........ r75605 | georg.brandl | 2009-10-22 13:48:10 +0200 (Do, 22 Okt 2009) | 1 line Use "impl-detail" directive where applicable. ........ r75606 | georg.brandl | 2009-10-22 17:00:06 +0200 (Do, 22 Okt 2009) | 1 line #6324: membership test tries iteration via __iter__. ........ r75607 | georg.brandl | 2009-10-22 17:04:09 +0200 (Do, 22 Okt 2009) | 1 line #7088: document new functions in signal as Unix-only. ........ r75610 | georg.brandl | 2009-10-22 17:27:24 +0200 (Do, 22 Okt 2009) | 1 line Reorder __slots__ fine print and add a clarification. ........ r75611 | georg.brandl | 2009-10-22 17:42:32 +0200 (Do, 22 Okt 2009) | 1 line #7035: improve docs of the various <method>_errors() functions, and give them docstrings. ........ r75612 | georg.brandl | 2009-10-22 17:52:15 +0200 (Do, 22 Okt 2009) | 1 line #7156: document curses as Unix-only. ........ r75613 | georg.brandl | 2009-10-22 17:54:35 +0200 (Do, 22 Okt 2009) | 1 line #6977: getopt does not support optional option arguments. ........ r75616 | georg.brandl | 2009-10-22 18:17:05 +0200 (Do, 22 Okt 2009) | 1 line Add proper references. ........ r75617 | georg.brandl | 2009-10-22 18:20:55 +0200 (Do, 22 Okt 2009) | 1 line Make printout margin important. ........ r75623 | georg.brandl | 2009-10-23 10:14:44 +0200 (Fr, 23 Okt 2009) | 1 line #7188: fix optionxform() docs. ........ r75627 | fred.drake | 2009-10-23 15:04:51 +0200 (Fr, 23 Okt 2009) | 2 lines add further note about what's passed to optionxform ........ r75640 | neil.schemenauer | 2009-10-23 21:58:17 +0200 (Fr, 23 Okt 2009) | 2 lines Improve some docstrings in the 'warnings' module. ........ r75647 | georg.brandl | 2009-10-24 12:04:19 +0200 (Sa, 24 Okt 2009) | 1 line Fix markup. ........ r75696 | georg.brandl | 2009-10-25 21:25:43 +0100 (So, 25 Okt 2009) | 1 line Fix a demo. ........ r75795 | georg.brandl | 2009-10-27 16:10:22 +0100 (Di, 27 Okt 2009) | 1 line Fix a strange mis-edit. ........
2009-10-27 12:28:25 -03:00
Availability: Unix.
.. function:: set_wakeup_fd(fd, *, warn_on_full_buffer=True)
Merged revisions 59565-59594 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r59568 | facundo.batista | 2007-12-19 13:53:01 +0100 (Wed, 19 Dec 2007) | 3 lines Some minor cleanups. Thanks Mark Dickinson. ........ r59573 | raymond.hettinger | 2007-12-19 19:13:31 +0100 (Wed, 19 Dec 2007) | 1 line Fix issue 1661: Flags argument silently ignored in re functions with compiled regexes. ........ r59574 | guido.van.rossum | 2007-12-19 20:41:06 +0100 (Wed, 19 Dec 2007) | 7 lines Patch #1583 by Adam Olsen. This adds signal.set_wakeup_fd(fd) which sets a file descriptor to which a zero byte will be written whenever a C exception handler runs. I added a simple C API as well, PySignal_SetWakeupFd(fd). ........ r59575 | raymond.hettinger | 2007-12-19 23:14:34 +0100 (Wed, 19 Dec 2007) | 1 line Bigger range for non-extended opargs. ........ r59576 | guido.van.rossum | 2007-12-19 23:51:13 +0100 (Wed, 19 Dec 2007) | 5 lines Patch #1549 by Thomas Herve. This changes the rules for when __hash__ is inherited slightly, by allowing it to be inherited when one or more of __lt__, __le__, __gt__, __ge__ are overridden, as long as __eq__ and __ne__ aren't. ........ r59577 | raymond.hettinger | 2007-12-20 02:25:05 +0100 (Thu, 20 Dec 2007) | 1 line Add comments ........ r59578 | brett.cannon | 2007-12-20 11:09:52 +0100 (Thu, 20 Dec 2007) | 3 lines Add tests for the warnings module; specifically formatwarning and showwarning. Still need tests for warn_explicit and simplefilter. ........ r59582 | guido.van.rossum | 2007-12-20 18:28:10 +0100 (Thu, 20 Dec 2007) | 2 lines Patch #1672 by Joseph Armbruster. Use tempdir() to get a temporary directory. ........ r59584 | georg.brandl | 2007-12-20 22:03:02 +0100 (Thu, 20 Dec 2007) | 2 lines Fix refleak introduced in r59576. ........ r59586 | guido.van.rossum | 2007-12-21 00:48:28 +0100 (Fri, 21 Dec 2007) | 4 lines Improve performance of built-in any()/all() by avoiding PyIter_Next() -- using a trick found in ifilter(). Feel free to backport to 2.5. ........ r59591 | andrew.kuchling | 2007-12-22 18:27:02 +0100 (Sat, 22 Dec 2007) | 1 line Add item ........
2007-12-24 04:52:31 -04:00
Set the wakeup file descriptor to *fd*. When a signal is received, the
signal number is written as a single byte into the fd. This can be used by
a library to wakeup a poll or select call, allowing the signal to be fully
processed.
Merged revisions 59565-59594 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r59568 | facundo.batista | 2007-12-19 13:53:01 +0100 (Wed, 19 Dec 2007) | 3 lines Some minor cleanups. Thanks Mark Dickinson. ........ r59573 | raymond.hettinger | 2007-12-19 19:13:31 +0100 (Wed, 19 Dec 2007) | 1 line Fix issue 1661: Flags argument silently ignored in re functions with compiled regexes. ........ r59574 | guido.van.rossum | 2007-12-19 20:41:06 +0100 (Wed, 19 Dec 2007) | 7 lines Patch #1583 by Adam Olsen. This adds signal.set_wakeup_fd(fd) which sets a file descriptor to which a zero byte will be written whenever a C exception handler runs. I added a simple C API as well, PySignal_SetWakeupFd(fd). ........ r59575 | raymond.hettinger | 2007-12-19 23:14:34 +0100 (Wed, 19 Dec 2007) | 1 line Bigger range for non-extended opargs. ........ r59576 | guido.van.rossum | 2007-12-19 23:51:13 +0100 (Wed, 19 Dec 2007) | 5 lines Patch #1549 by Thomas Herve. This changes the rules for when __hash__ is inherited slightly, by allowing it to be inherited when one or more of __lt__, __le__, __gt__, __ge__ are overridden, as long as __eq__ and __ne__ aren't. ........ r59577 | raymond.hettinger | 2007-12-20 02:25:05 +0100 (Thu, 20 Dec 2007) | 1 line Add comments ........ r59578 | brett.cannon | 2007-12-20 11:09:52 +0100 (Thu, 20 Dec 2007) | 3 lines Add tests for the warnings module; specifically formatwarning and showwarning. Still need tests for warn_explicit and simplefilter. ........ r59582 | guido.van.rossum | 2007-12-20 18:28:10 +0100 (Thu, 20 Dec 2007) | 2 lines Patch #1672 by Joseph Armbruster. Use tempdir() to get a temporary directory. ........ r59584 | georg.brandl | 2007-12-20 22:03:02 +0100 (Thu, 20 Dec 2007) | 2 lines Fix refleak introduced in r59576. ........ r59586 | guido.van.rossum | 2007-12-21 00:48:28 +0100 (Fri, 21 Dec 2007) | 4 lines Improve performance of built-in any()/all() by avoiding PyIter_Next() -- using a trick found in ifilter(). Feel free to backport to 2.5. ........ r59591 | andrew.kuchling | 2007-12-22 18:27:02 +0100 (Sat, 22 Dec 2007) | 1 line Add item ........
2007-12-24 04:52:31 -04:00
The old wakeup fd is returned (or -1 if file descriptor wakeup was not
enabled). If *fd* is -1, file descriptor wakeup is disabled.
If not -1, *fd* must be non-blocking. It is up to the library to remove
any bytes from *fd* before calling poll or select again.
Merged revisions 59565-59594 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r59568 | facundo.batista | 2007-12-19 13:53:01 +0100 (Wed, 19 Dec 2007) | 3 lines Some minor cleanups. Thanks Mark Dickinson. ........ r59573 | raymond.hettinger | 2007-12-19 19:13:31 +0100 (Wed, 19 Dec 2007) | 1 line Fix issue 1661: Flags argument silently ignored in re functions with compiled regexes. ........ r59574 | guido.van.rossum | 2007-12-19 20:41:06 +0100 (Wed, 19 Dec 2007) | 7 lines Patch #1583 by Adam Olsen. This adds signal.set_wakeup_fd(fd) which sets a file descriptor to which a zero byte will be written whenever a C exception handler runs. I added a simple C API as well, PySignal_SetWakeupFd(fd). ........ r59575 | raymond.hettinger | 2007-12-19 23:14:34 +0100 (Wed, 19 Dec 2007) | 1 line Bigger range for non-extended opargs. ........ r59576 | guido.van.rossum | 2007-12-19 23:51:13 +0100 (Wed, 19 Dec 2007) | 5 lines Patch #1549 by Thomas Herve. This changes the rules for when __hash__ is inherited slightly, by allowing it to be inherited when one or more of __lt__, __le__, __gt__, __ge__ are overridden, as long as __eq__ and __ne__ aren't. ........ r59577 | raymond.hettinger | 2007-12-20 02:25:05 +0100 (Thu, 20 Dec 2007) | 1 line Add comments ........ r59578 | brett.cannon | 2007-12-20 11:09:52 +0100 (Thu, 20 Dec 2007) | 3 lines Add tests for the warnings module; specifically formatwarning and showwarning. Still need tests for warn_explicit and simplefilter. ........ r59582 | guido.van.rossum | 2007-12-20 18:28:10 +0100 (Thu, 20 Dec 2007) | 2 lines Patch #1672 by Joseph Armbruster. Use tempdir() to get a temporary directory. ........ r59584 | georg.brandl | 2007-12-20 22:03:02 +0100 (Thu, 20 Dec 2007) | 2 lines Fix refleak introduced in r59576. ........ r59586 | guido.van.rossum | 2007-12-21 00:48:28 +0100 (Fri, 21 Dec 2007) | 4 lines Improve performance of built-in any()/all() by avoiding PyIter_Next() -- using a trick found in ifilter(). Feel free to backport to 2.5. ........ r59591 | andrew.kuchling | 2007-12-22 18:27:02 +0100 (Sat, 22 Dec 2007) | 1 line Add item ........
2007-12-24 04:52:31 -04:00
When threads are enabled, this function can only be called from the main thread;
attempting to call it from other threads will cause a :exc:`ValueError`
exception to be raised.
There are two common ways to use this function. In both approaches,
you use the fd to wake up when a signal arrives, but then they
differ in how they determine *which* signal or signals have
arrived.
In the first approach, we read the data out of the fd's buffer, and
the byte values give you the signal numbers. This is simple, but in
rare cases it can run into a problem: generally the fd will have a
limited amount of buffer space, and if too many signals arrive too
quickly, then the buffer may become full, and some signals may be
lost. If you use this approach, then you should set
``warn_on_full_buffer=True``, which will at least cause a warning
to be printed to stderr when signals are lost.
In the second approach, we use the wakeup fd *only* for wakeups,
and ignore the actual byte values. In this case, all we care about
is whether the fd's buffer is empty or non-empty; a full buffer
doesn't indicate a problem at all. If you use this approach, then
you should set ``warn_on_full_buffer=False``, so that your users
are not confused by spurious warning messages.
.. versionchanged:: 3.5
On Windows, the function now also supports socket handles.
.. versionchanged:: 3.7
Added ``warn_on_full_buffer`` parameter.
Merged revisions 59565-59594 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r59568 | facundo.batista | 2007-12-19 13:53:01 +0100 (Wed, 19 Dec 2007) | 3 lines Some minor cleanups. Thanks Mark Dickinson. ........ r59573 | raymond.hettinger | 2007-12-19 19:13:31 +0100 (Wed, 19 Dec 2007) | 1 line Fix issue 1661: Flags argument silently ignored in re functions with compiled regexes. ........ r59574 | guido.van.rossum | 2007-12-19 20:41:06 +0100 (Wed, 19 Dec 2007) | 7 lines Patch #1583 by Adam Olsen. This adds signal.set_wakeup_fd(fd) which sets a file descriptor to which a zero byte will be written whenever a C exception handler runs. I added a simple C API as well, PySignal_SetWakeupFd(fd). ........ r59575 | raymond.hettinger | 2007-12-19 23:14:34 +0100 (Wed, 19 Dec 2007) | 1 line Bigger range for non-extended opargs. ........ r59576 | guido.van.rossum | 2007-12-19 23:51:13 +0100 (Wed, 19 Dec 2007) | 5 lines Patch #1549 by Thomas Herve. This changes the rules for when __hash__ is inherited slightly, by allowing it to be inherited when one or more of __lt__, __le__, __gt__, __ge__ are overridden, as long as __eq__ and __ne__ aren't. ........ r59577 | raymond.hettinger | 2007-12-20 02:25:05 +0100 (Thu, 20 Dec 2007) | 1 line Add comments ........ r59578 | brett.cannon | 2007-12-20 11:09:52 +0100 (Thu, 20 Dec 2007) | 3 lines Add tests for the warnings module; specifically formatwarning and showwarning. Still need tests for warn_explicit and simplefilter. ........ r59582 | guido.van.rossum | 2007-12-20 18:28:10 +0100 (Thu, 20 Dec 2007) | 2 lines Patch #1672 by Joseph Armbruster. Use tempdir() to get a temporary directory. ........ r59584 | georg.brandl | 2007-12-20 22:03:02 +0100 (Thu, 20 Dec 2007) | 2 lines Fix refleak introduced in r59576. ........ r59586 | guido.van.rossum | 2007-12-21 00:48:28 +0100 (Fri, 21 Dec 2007) | 4 lines Improve performance of built-in any()/all() by avoiding PyIter_Next() -- using a trick found in ifilter(). Feel free to backport to 2.5. ........ r59591 | andrew.kuchling | 2007-12-22 18:27:02 +0100 (Sat, 22 Dec 2007) | 1 line Add item ........
2007-12-24 04:52:31 -04:00
Merged revisions 60481,60485,60489-60492,60494-60496,60498-60499,60501-60503,60505-60506,60508-60509,60523-60524,60532,60543,60545,60547-60548,60552,60554,60556-60559,60561-60562,60569,60571-60572,60574,60576-60583,60585-60586,60589,60591,60594-60595,60597-60598,60600-60601,60606-60612,60615,60617,60619-60621,60623-60625,60627-60629,60631,60633,60635,60647,60650,60652,60654,60656,60658-60659,60664-60666,60668-60670,60672,60676,60678,60680-60683,60685-60686,60688,60690,60692-60694,60697-60700,60705-60706,60708,60711,60714,60720,60724-60730,60732,60736,60742,60744,60746,60748,60750-60751,60753,60756-60757,60759-60761,60763-60764,60766,60769-60770,60774-60784,60787-60789,60793,60796,60799-60809,60812-60813,60815-60821,60823-60826,60828-60829,60831-60834,60836,60838-60839,60846-60849,60852-60854,60856-60859,60861-60870,60874-60875,60880-60881,60886,60888-60890,60892,60894-60898,60900,60902-60906,60908,60911-60917,60919-60920,60922,60926,60929-60931,60933-60935,60937,60939-60941,60943-60954,60959-60961,60963-60964,60966-60967,60971,60977,60979-60989 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r60980 | georg.brandl | 2008-02-23 16:02:28 +0100 (Sat, 23 Feb 2008) | 2 lines #1492: allow overriding BaseHTTPServer's content type for error messages. ........ r60982 | georg.brandl | 2008-02-23 16:06:25 +0100 (Sat, 23 Feb 2008) | 2 lines #2165: fix test_logging failure on some machines. ........ r60983 | facundo.batista | 2008-02-23 16:07:35 +0100 (Sat, 23 Feb 2008) | 6 lines Issue 1089358. Adds the siginterrupt() function, that is just a wrapper around the system call with the same name. Also added test cases, doc changes and NEWS entry. Thanks Jason and Ralf Schmitt. ........ r60984 | georg.brandl | 2008-02-23 16:11:18 +0100 (Sat, 23 Feb 2008) | 2 lines #2067: file.__exit__() now calls subclasses' close() method. ........ r60985 | georg.brandl | 2008-02-23 16:19:54 +0100 (Sat, 23 Feb 2008) | 2 lines More difflib examples. Written for GHOP by Josip Dzolonga. ........ r60987 | andrew.kuchling | 2008-02-23 16:41:51 +0100 (Sat, 23 Feb 2008) | 1 line #2072: correct documentation for .rpc_paths ........ r60988 | georg.brandl | 2008-02-23 16:43:48 +0100 (Sat, 23 Feb 2008) | 2 lines #2161: Fix opcode name. ........ r60989 | andrew.kuchling | 2008-02-23 16:49:35 +0100 (Sat, 23 Feb 2008) | 2 lines #1119331: ncurses will just call exit() if the terminal name isn't found. Call setupterm() first so that we get a Python exception instead of just existing. ........
2008-02-23 12:23:06 -04:00
.. function:: siginterrupt(signalnum, flag)
Change system call restart behaviour: if *flag* is :const:`False`, system
calls will be restarted when interrupted by signal *signalnum*, otherwise
Merged revisions 75365,75394,75402-75403,75418,75459,75484,75592-75596,75600,75602-75607,75610-75613,75616-75617,75623,75627,75640,75647,75696,75795 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r75365 | georg.brandl | 2009-10-11 22:16:16 +0200 (So, 11 Okt 2009) | 1 line Fix broken links found by "make linkcheck". scipy.org seems to be done right now, so I could not verify links going there. ........ r75394 | georg.brandl | 2009-10-13 20:10:59 +0200 (Di, 13 Okt 2009) | 1 line Fix markup. ........ r75402 | georg.brandl | 2009-10-14 17:51:48 +0200 (Mi, 14 Okt 2009) | 1 line #7125: fix typo. ........ r75403 | georg.brandl | 2009-10-14 17:57:46 +0200 (Mi, 14 Okt 2009) | 1 line #7126: os.environ changes *do* take effect in subprocesses started with os.system(). ........ r75418 | georg.brandl | 2009-10-14 20:48:32 +0200 (Mi, 14 Okt 2009) | 1 line #7116: str.join() takes an iterable. ........ r75459 | georg.brandl | 2009-10-17 10:57:43 +0200 (Sa, 17 Okt 2009) | 1 line Fix refleaks in _ctypes PyCSimpleType_New, which fixes the refleak seen in test___all__. ........ r75484 | georg.brandl | 2009-10-18 09:58:12 +0200 (So, 18 Okt 2009) | 1 line Fix missing word. ........ r75592 | georg.brandl | 2009-10-22 09:05:48 +0200 (Do, 22 Okt 2009) | 1 line Fix punctuation. ........ r75593 | georg.brandl | 2009-10-22 09:06:49 +0200 (Do, 22 Okt 2009) | 1 line Revert unintended change. ........ r75594 | georg.brandl | 2009-10-22 09:56:02 +0200 (Do, 22 Okt 2009) | 1 line Fix markup. ........ r75595 | georg.brandl | 2009-10-22 09:56:56 +0200 (Do, 22 Okt 2009) | 1 line Fix duplicate target. ........ r75596 | georg.brandl | 2009-10-22 10:05:04 +0200 (Do, 22 Okt 2009) | 1 line Add a new directive marking up implementation details and start using it. ........ r75600 | georg.brandl | 2009-10-22 13:01:46 +0200 (Do, 22 Okt 2009) | 1 line Make it more robust. ........ r75602 | georg.brandl | 2009-10-22 13:28:06 +0200 (Do, 22 Okt 2009) | 1 line Document new directive. ........ r75603 | georg.brandl | 2009-10-22 13:28:23 +0200 (Do, 22 Okt 2009) | 1 line Allow short form with text as argument. ........ r75604 | georg.brandl | 2009-10-22 13:36:50 +0200 (Do, 22 Okt 2009) | 1 line Fix stylesheet for multi-paragraph impl-details. ........ r75605 | georg.brandl | 2009-10-22 13:48:10 +0200 (Do, 22 Okt 2009) | 1 line Use "impl-detail" directive where applicable. ........ r75606 | georg.brandl | 2009-10-22 17:00:06 +0200 (Do, 22 Okt 2009) | 1 line #6324: membership test tries iteration via __iter__. ........ r75607 | georg.brandl | 2009-10-22 17:04:09 +0200 (Do, 22 Okt 2009) | 1 line #7088: document new functions in signal as Unix-only. ........ r75610 | georg.brandl | 2009-10-22 17:27:24 +0200 (Do, 22 Okt 2009) | 1 line Reorder __slots__ fine print and add a clarification. ........ r75611 | georg.brandl | 2009-10-22 17:42:32 +0200 (Do, 22 Okt 2009) | 1 line #7035: improve docs of the various <method>_errors() functions, and give them docstrings. ........ r75612 | georg.brandl | 2009-10-22 17:52:15 +0200 (Do, 22 Okt 2009) | 1 line #7156: document curses as Unix-only. ........ r75613 | georg.brandl | 2009-10-22 17:54:35 +0200 (Do, 22 Okt 2009) | 1 line #6977: getopt does not support optional option arguments. ........ r75616 | georg.brandl | 2009-10-22 18:17:05 +0200 (Do, 22 Okt 2009) | 1 line Add proper references. ........ r75617 | georg.brandl | 2009-10-22 18:20:55 +0200 (Do, 22 Okt 2009) | 1 line Make printout margin important. ........ r75623 | georg.brandl | 2009-10-23 10:14:44 +0200 (Fr, 23 Okt 2009) | 1 line #7188: fix optionxform() docs. ........ r75627 | fred.drake | 2009-10-23 15:04:51 +0200 (Fr, 23 Okt 2009) | 2 lines add further note about what's passed to optionxform ........ r75640 | neil.schemenauer | 2009-10-23 21:58:17 +0200 (Fr, 23 Okt 2009) | 2 lines Improve some docstrings in the 'warnings' module. ........ r75647 | georg.brandl | 2009-10-24 12:04:19 +0200 (Sa, 24 Okt 2009) | 1 line Fix markup. ........ r75696 | georg.brandl | 2009-10-25 21:25:43 +0100 (So, 25 Okt 2009) | 1 line Fix a demo. ........ r75795 | georg.brandl | 2009-10-27 16:10:22 +0100 (Di, 27 Okt 2009) | 1 line Fix a strange mis-edit. ........
2009-10-27 12:28:25 -03:00
system calls will be interrupted. Returns nothing. Availability: Unix (see
the man page :manpage:`siginterrupt(3)` for further information).
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Note that installing a signal handler with :func:`signal` will reset the
restart behaviour to interruptible by implicitly calling
:c:func:`siginterrupt` with a true *flag* value for the given signal.
Merged revisions 60481,60485,60489-60492,60494-60496,60498-60499,60501-60503,60505-60506,60508-60509,60523-60524,60532,60543,60545,60547-60548,60552,60554,60556-60559,60561-60562,60569,60571-60572,60574,60576-60583,60585-60586,60589,60591,60594-60595,60597-60598,60600-60601,60606-60612,60615,60617,60619-60621,60623-60625,60627-60629,60631,60633,60635,60647,60650,60652,60654,60656,60658-60659,60664-60666,60668-60670,60672,60676,60678,60680-60683,60685-60686,60688,60690,60692-60694,60697-60700,60705-60706,60708,60711,60714,60720,60724-60730,60732,60736,60742,60744,60746,60748,60750-60751,60753,60756-60757,60759-60761,60763-60764,60766,60769-60770,60774-60784,60787-60789,60793,60796,60799-60809,60812-60813,60815-60821,60823-60826,60828-60829,60831-60834,60836,60838-60839,60846-60849,60852-60854,60856-60859,60861-60870,60874-60875,60880-60881,60886,60888-60890,60892,60894-60898,60900,60902-60906,60908,60911-60917,60919-60920,60922,60926,60929-60931,60933-60935,60937,60939-60941,60943-60954,60959-60961,60963-60964,60966-60967,60971,60977,60979-60989 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r60980 | georg.brandl | 2008-02-23 16:02:28 +0100 (Sat, 23 Feb 2008) | 2 lines #1492: allow overriding BaseHTTPServer's content type for error messages. ........ r60982 | georg.brandl | 2008-02-23 16:06:25 +0100 (Sat, 23 Feb 2008) | 2 lines #2165: fix test_logging failure on some machines. ........ r60983 | facundo.batista | 2008-02-23 16:07:35 +0100 (Sat, 23 Feb 2008) | 6 lines Issue 1089358. Adds the siginterrupt() function, that is just a wrapper around the system call with the same name. Also added test cases, doc changes and NEWS entry. Thanks Jason and Ralf Schmitt. ........ r60984 | georg.brandl | 2008-02-23 16:11:18 +0100 (Sat, 23 Feb 2008) | 2 lines #2067: file.__exit__() now calls subclasses' close() method. ........ r60985 | georg.brandl | 2008-02-23 16:19:54 +0100 (Sat, 23 Feb 2008) | 2 lines More difflib examples. Written for GHOP by Josip Dzolonga. ........ r60987 | andrew.kuchling | 2008-02-23 16:41:51 +0100 (Sat, 23 Feb 2008) | 1 line #2072: correct documentation for .rpc_paths ........ r60988 | georg.brandl | 2008-02-23 16:43:48 +0100 (Sat, 23 Feb 2008) | 2 lines #2161: Fix opcode name. ........ r60989 | andrew.kuchling | 2008-02-23 16:49:35 +0100 (Sat, 23 Feb 2008) | 2 lines #1119331: ncurses will just call exit() if the terminal name isn't found. Call setupterm() first so that we get a Python exception instead of just existing. ........
2008-02-23 12:23:06 -04:00
2007-08-15 11:28:22 -03:00
.. function:: signal(signalnum, handler)
Set the handler for signal *signalnum* to the function *handler*. *handler* can
be a callable Python object taking two arguments (see below), or one of the
special values :const:`signal.SIG_IGN` or :const:`signal.SIG_DFL`. The previous
signal handler will be returned (see the description of :func:`getsignal`
above). (See the Unix man page :manpage:`signal(2)`.)
When threads are enabled, this function can only be called from the main thread;
attempting to call it from other threads will cause a :exc:`ValueError`
exception to be raised.
The *handler* is called with two arguments: the signal number and the current
Merged revisions 74542,74544-74548,74550,74554-74555,74578,74588,74590,74603,74616-74618,74621 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r74542 | georg.brandl | 2009-08-23 23:28:56 +0200 (So, 23 Aug 2009) | 1 line Restore alphabetic order. ........ r74544 | georg.brandl | 2009-08-24 19:12:30 +0200 (Mo, 24 Aug 2009) | 1 line #6775: fix python.org URLs in README. ........ r74545 | georg.brandl | 2009-08-24 19:14:29 +0200 (Mo, 24 Aug 2009) | 1 line #6772: mention utf-8 as utf8 alias. ........ r74546 | georg.brandl | 2009-08-24 19:20:40 +0200 (Mo, 24 Aug 2009) | 1 line #6725: spell "namespace" consistently. ........ r74547 | georg.brandl | 2009-08-24 19:22:05 +0200 (Mo, 24 Aug 2009) | 1 line #6718: fix example. ........ r74548 | georg.brandl | 2009-08-24 19:24:27 +0200 (Mo, 24 Aug 2009) | 1 line #6677: mention "deleting" as an alias for removing files. ........ r74550 | georg.brandl | 2009-08-24 19:48:40 +0200 (Mo, 24 Aug 2009) | 1 line #6677: note that rmdir only removes empty directories. ........ r74554 | georg.brandl | 2009-08-27 20:59:02 +0200 (Do, 27 Aug 2009) | 1 line Typo fix. ........ r74555 | georg.brandl | 2009-08-27 21:02:43 +0200 (Do, 27 Aug 2009) | 1 line #6787: reference fix. ........ r74578 | tarek.ziade | 2009-08-29 15:33:21 +0200 (Sa, 29 Aug 2009) | 1 line fixed #6801: symmetric_difference_update also accepts pipe ........ r74588 | georg.brandl | 2009-08-30 10:35:01 +0200 (So, 30 Aug 2009) | 1 line #6803: fix old name. ........ r74590 | georg.brandl | 2009-08-30 13:51:53 +0200 (So, 30 Aug 2009) | 1 line #6801: fix copy-paste oversight. ........ r74603 | georg.brandl | 2009-08-31 08:38:29 +0200 (Mo, 31 Aug 2009) | 1 line other -> others where multiple arguments are accepted. ........ r74616 | georg.brandl | 2009-09-01 09:46:26 +0200 (Di, 01 Sep 2009) | 1 line #6808: clarification. ........ r74617 | georg.brandl | 2009-09-01 09:53:37 +0200 (Di, 01 Sep 2009) | 1 line #6765: hint that log(x, base) is not very sophisticated. ........ r74618 | georg.brandl | 2009-09-01 10:00:47 +0200 (Di, 01 Sep 2009) | 1 line #6810: add a link to the section about frame objects instead of just a description where to find it. ........ r74621 | georg.brandl | 2009-09-01 10:06:03 +0200 (Di, 01 Sep 2009) | 1 line #6638: fix wrong parameter name and markup a class. ........
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stack frame (``None`` or a frame object; for a description of frame objects,
see the :ref:`description in the type hierarchy <frame-objects>` or see the
attribute descriptions in the :mod:`inspect` module).
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On Windows, :func:`signal` can only be called with :const:`SIGABRT`,
:const:`SIGFPE`, :const:`SIGILL`, :const:`SIGINT`, :const:`SIGSEGV`,
:const:`SIGTERM`, or :const:`SIGBREAK`.
A :exc:`ValueError` will be raised in any other case.
Note that not all systems define the same set of signal names; an
:exc:`AttributeError` will be raised if a signal name is not defined as
``SIG*`` module level constant.
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.. function:: sigpending()
Examine the set of signals that are pending for delivery to the calling
thread (i.e., the signals which have been raised while blocked). Return the
set of the pending signals.
Availability: Unix (see the man page :manpage:`sigpending(2)` for further
information).
See also :func:`pause`, :func:`pthread_sigmask` and :func:`sigwait`.
.. versionadded:: 3.3
.. function:: sigwait(sigset)
Suspend execution of the calling thread until the delivery of one of the
signals specified in the signal set *sigset*. The function accepts the signal
(removes it from the pending list of signals), and returns the signal number.
Availability: Unix (see the man page :manpage:`sigwait(3)` for further
information).
See also :func:`pause`, :func:`pthread_sigmask`, :func:`sigpending`,
:func:`sigwaitinfo` and :func:`sigtimedwait`.
.. versionadded:: 3.3
.. function:: sigwaitinfo(sigset)
Suspend execution of the calling thread until the delivery of one of the
signals specified in the signal set *sigset*. The function accepts the
signal and removes it from the pending list of signals. If one of the
signals in *sigset* is already pending for the calling thread, the function
will return immediately with information about that signal. The signal
handler is not called for the delivered signal. The function raises an
:exc:`InterruptedError` if it is interrupted by a signal that is not in
*sigset*.
The return value is an object representing the data contained in the
:c:type:`siginfo_t` structure, namely: :attr:`si_signo`, :attr:`si_code`,
:attr:`si_errno`, :attr:`si_pid`, :attr:`si_uid`, :attr:`si_status`,
:attr:`si_band`.
Availability: Unix (see the man page :manpage:`sigwaitinfo(2)` for further
information).
See also :func:`pause`, :func:`sigwait` and :func:`sigtimedwait`.
.. versionadded:: 3.3
.. versionchanged:: 3.5
The function is now retried if interrupted by a signal not in *sigset*
and the signal handler does not raise an exception (see :pep:`475` for
the rationale).
.. function:: sigtimedwait(sigset, timeout)
Like :func:`sigwaitinfo`, but takes an additional *timeout* argument
specifying a timeout. If *timeout* is specified as :const:`0`, a poll is
performed. Returns :const:`None` if a timeout occurs.
Availability: Unix (see the man page :manpage:`sigtimedwait(2)` for further
information).
See also :func:`pause`, :func:`sigwait` and :func:`sigwaitinfo`.
.. versionadded:: 3.3
.. versionchanged:: 3.5
The function is now retried with the recomputed *timeout* if interrupted
by a signal not in *sigset* and the signal handler does not raise an
exception (see :pep:`475` for the rationale).
2007-08-15 11:28:22 -03:00
.. _signal-example:
Example
-------
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
serial device that may not be turned on, which would normally cause the
:func:`os.open` to hang indefinitely. The solution is to set a 5-second alarm
before opening the file; if the operation takes too long, the alarm signal will
be sent, and the handler raises an exception. ::
import signal, os
def handler(signum, frame):
print('Signal handler called with signal', signum)
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raise OSError("Couldn't open device!")
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# Set the signal handler and a 5-second alarm
signal.signal(signal.SIGALRM, handler)
signal.alarm(5)
# This open() may hang indefinitely
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fd = os.open('/dev/ttyS0', os.O_RDWR)
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signal.alarm(0) # Disable the alarm
Note on SIGPIPE
---------------
Piping output of your program to tools like :manpage:`head(1)` will
cause a :const:`SIGPIPE` signal to be sent to your process when the receiver
of its standard output closes early. This results in an exception
like :code:`BrokenPipeError: [Errno 32] Broken pipe`. To handle this
case, wrap your entry point to catch this exception as follows::
import os
import sys
def main():
try:
# simulate large output (your code replaces this loop)
for x in range(10000):
print("y")
# flush output here to force SIGPIPE to be triggered
# while inside this try block.
sys.stdout.flush()
except BrokenPipeError:
# Python flushes standard streams on exit; redirect remaining output
# to devnull to avoid another BrokenPipeError at shutdown
devnull = os.open(os.devnull, os.O_WRONLY)
os.dup2(devnull, sys.stdout.fileno())
sys.exit(1) # Python exits with error code 1 on EPIPE
if __name__ == '__main__':
main()
Do not set :const:`SIGPIPE`'s disposition to :const:`SIG_DFL`
in order to avoid :exc:`BrokenPipeError`. Doing that would cause
your program to exit unexpectedly also whenever any socket connection
is interrupted while your program is still writing to it.