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| .. highlight:: c
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| 
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| .. _c-api-monitoring:
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| 
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| Monitoring C API
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| ================
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| 
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| Added in version 3.13.
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| 
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| An extension may need to interact with the event monitoring system. Subscribing
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| to events and registering callbacks can be done via the Python API exposed in
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| :mod:`sys.monitoring`.
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| 
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| Generating Execution Events
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| ===========================
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| 
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| The functions below make it possible for an extension to fire monitoring
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| events as it emulates the execution of Python code. Each of these functions
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| accepts a ``PyMonitoringState`` struct which contains concise information
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| about the activation state of events, as well as the event arguments, which
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| include a ``PyObject*`` representing the code object, the instruction offset
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| and sometimes additional, event-specific arguments (see :mod:`sys.monitoring`
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| for details about the signatures of the different event callbacks).
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| The ``codelike`` argument should be an instance of :class:`types.CodeType`
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| or of a type that emulates it.
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| 
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| The VM disables tracing when firing an event, so there is no need for user
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| code to do that.
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| 
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| Monitoring functions should not be called with an exception set,
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| except those listed below as working with the current exception.
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| 
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| .. c:type:: PyMonitoringState
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| 
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|   Representation of the state of an event type. It is allocated by the user
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|   while its contents are maintained by the monitoring API functions described below.
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| 
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| 
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| All of the functions below return 0 on success and -1 (with an exception set) on error.
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| 
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| See :mod:`sys.monitoring` for descriptions of the events.
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| 
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| .. c:function:: int PyMonitoring_FirePyStartEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset)
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| 
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|    Fire a ``PY_START`` event.
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| 
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| 
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| .. c:function:: int PyMonitoring_FirePyResumeEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset)
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| 
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|    Fire a ``PY_RESUME`` event.
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| 
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| 
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| .. c:function:: int PyMonitoring_FirePyReturnEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset, PyObject* retval)
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| 
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|    Fire a ``PY_RETURN`` event.
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| 
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| 
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| .. c:function:: int PyMonitoring_FirePyYieldEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset, PyObject* retval)
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| 
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|    Fire a ``PY_YIELD`` event.
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| 
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| 
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| .. c:function:: int PyMonitoring_FireCallEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset, PyObject* callable, PyObject *arg0)
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| 
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|    Fire a ``CALL`` event.
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| 
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| 
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| .. c:function:: int PyMonitoring_FireLineEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset, int lineno)
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| 
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|    Fire a ``LINE`` event.
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| 
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| 
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| .. c:function:: int PyMonitoring_FireJumpEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset, PyObject *target_offset)
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| 
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|    Fire a ``JUMP`` event.
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| 
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| 
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| .. c:function:: int PyMonitoring_FireBranchLeftEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset, PyObject *target_offset)
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| 
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|    Fire a ``BRANCH_LEFT`` event.
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| 
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| 
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| .. c:function:: int PyMonitoring_FireBranchRightEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset, PyObject *target_offset)
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| 
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|    Fire a ``BRANCH_RIGHT`` event.
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| 
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| 
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| .. c:function:: int PyMonitoring_FireCReturnEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset, PyObject *retval)
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| 
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|    Fire a ``C_RETURN`` event.
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| 
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| 
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| .. c:function:: int PyMonitoring_FirePyThrowEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset)
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| 
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|    Fire a ``PY_THROW`` event with the current exception (as returned by
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|    :c:func:`PyErr_GetRaisedException`).
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| 
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| 
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| .. c:function:: int PyMonitoring_FireRaiseEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset)
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| 
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|    Fire a ``RAISE`` event with the current exception (as returned by
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|    :c:func:`PyErr_GetRaisedException`).
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| 
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| 
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| .. c:function:: int PyMonitoring_FireCRaiseEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset)
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| 
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|    Fire a ``C_RAISE`` event with the current exception (as returned by
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|    :c:func:`PyErr_GetRaisedException`).
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| 
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| 
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| .. c:function:: int PyMonitoring_FireReraiseEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset)
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| 
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|    Fire a ``RERAISE`` event with the current exception (as returned by
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|    :c:func:`PyErr_GetRaisedException`).
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| 
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| 
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| .. c:function:: int PyMonitoring_FireExceptionHandledEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset)
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| 
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|    Fire an ``EXCEPTION_HANDLED`` event with the current exception (as returned by
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|    :c:func:`PyErr_GetRaisedException`).
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| 
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| 
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| .. c:function:: int PyMonitoring_FirePyUnwindEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset)
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| 
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|    Fire a ``PY_UNWIND`` event with the current exception (as returned by
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|    :c:func:`PyErr_GetRaisedException`).
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| 
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| 
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| .. c:function:: int PyMonitoring_FireStopIterationEvent(PyMonitoringState *state, PyObject *codelike, int32_t offset, PyObject *value)
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| 
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|    Fire a ``STOP_ITERATION`` event. If ``value`` is an instance of :exc:`StopIteration`, it is used. Otherwise,
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|    a new :exc:`StopIteration` instance is created with ``value`` as its argument.
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| 
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| 
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| Managing the Monitoring State
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| -----------------------------
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| 
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| Monitoring states can be managed with the help of monitoring scopes. A scope
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| would typically correspond to a python function.
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| 
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| .. c:function:: int PyMonitoring_EnterScope(PyMonitoringState *state_array, uint64_t *version, const uint8_t *event_types, Py_ssize_t length)
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| 
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|    Enter a monitored scope. ``event_types`` is an array of the event IDs for
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|    events that may be fired from the scope. For example, the ID of a ``PY_START``
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|    event is the value ``PY_MONITORING_EVENT_PY_START``, which is numerically equal
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|    to the base-2 logarithm of ``sys.monitoring.events.PY_START``.
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|    ``state_array`` is an array with a monitoring state entry for each event in
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|    ``event_types``, it is allocated by the user but populated by
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|    :c:func:`!PyMonitoring_EnterScope` with information about the activation state of
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|    the event. The size of ``event_types`` (and hence also of ``state_array``)
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|    is given in ``length``.
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| 
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|    The ``version`` argument is a pointer to a value which should be allocated
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|    by the user together with ``state_array`` and initialized to 0,
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|    and then set only by :c:func:`!PyMonitoring_EnterScope` itself. It allows this
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|    function to determine whether event states have changed since the previous call,
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|    and to return quickly if they have not.
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| 
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|    The scopes referred to here are lexical scopes: a function, class or method.
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|    :c:func:`!PyMonitoring_EnterScope` should be called whenever the lexical scope is
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|    entered. Scopes can be reentered, reusing the same *state_array* and *version*,
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|    in situations like when emulating a recursive Python function. When a code-like's
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|    execution is paused, such as when emulating a generator, the scope needs to
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|    be exited and re-entered.
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| 
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|    The macros for *event_types* are:
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| 
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|    .. c:namespace:: NULL
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| 
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|    .. The table is here to make the docs searchable, and to allow automatic
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|       links to the identifiers.
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| 
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|    ================================================== =====================================
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|    Macro                                              Event
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|    ================================================== =====================================
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|    .. c:macro:: PY_MONITORING_EVENT_BRANCH_LEFT       :monitoring-event:`BRANCH_LEFT`
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|    .. c:macro:: PY_MONITORING_EVENT_BRANCH_RIGHT      :monitoring-event:`BRANCH_RIGHT`
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|    .. c:macro:: PY_MONITORING_EVENT_CALL              :monitoring-event:`CALL`
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|    .. c:macro:: PY_MONITORING_EVENT_C_RAISE           :monitoring-event:`C_RAISE`
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|    .. c:macro:: PY_MONITORING_EVENT_C_RETURN          :monitoring-event:`C_RETURN`
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|    .. c:macro:: PY_MONITORING_EVENT_EXCEPTION_HANDLED :monitoring-event:`EXCEPTION_HANDLED`
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|    .. c:macro:: PY_MONITORING_EVENT_INSTRUCTION       :monitoring-event:`INSTRUCTION`
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|    .. c:macro:: PY_MONITORING_EVENT_JUMP              :monitoring-event:`JUMP`
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|    .. c:macro:: PY_MONITORING_EVENT_LINE              :monitoring-event:`LINE`
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|    .. c:macro:: PY_MONITORING_EVENT_PY_RESUME         :monitoring-event:`PY_RESUME`
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|    .. c:macro:: PY_MONITORING_EVENT_PY_RETURN         :monitoring-event:`PY_RETURN`
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|    .. c:macro:: PY_MONITORING_EVENT_PY_START          :monitoring-event:`PY_START`
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|    .. c:macro:: PY_MONITORING_EVENT_PY_THROW          :monitoring-event:`PY_THROW`
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|    .. c:macro:: PY_MONITORING_EVENT_PY_UNWIND         :monitoring-event:`PY_UNWIND`
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|    .. c:macro:: PY_MONITORING_EVENT_PY_YIELD          :monitoring-event:`PY_YIELD`
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|    .. c:macro:: PY_MONITORING_EVENT_RAISE             :monitoring-event:`RAISE`
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|    .. c:macro:: PY_MONITORING_EVENT_RERAISE           :monitoring-event:`RERAISE`
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|    .. c:macro:: PY_MONITORING_EVENT_STOP_ITERATION    :monitoring-event:`STOP_ITERATION`
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|    ================================================== =====================================
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| 
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| .. c:function:: int PyMonitoring_ExitScope(void)
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| 
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|    Exit the last scope that was entered with :c:func:`!PyMonitoring_EnterScope`.
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| 
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| 
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| .. c:function:: int PY_MONITORING_IS_INSTRUMENTED_EVENT(uint8_t ev)
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| 
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|    Return true if the event corresponding to the event ID *ev* is
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|    a :ref:`local event <monitoring-event-local>`.
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| 
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|    .. versionadded:: 3.13
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| 
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|    .. deprecated:: 3.14
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| 
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|       This function is :term:`soft deprecated`.
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