EP 454: reformat
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Victor Stinner
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pep-0454.txt
215
pep-0454.txt
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@ -13,7 +13,7 @@ Python-Version: 3.4
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Abstract
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========
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Add a new tracemalloc module to trace Python memory allocations.
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Add a new ``tracemalloc`` module to trace Python memory allocations.
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@ -29,6 +29,14 @@ information:
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* Compute delta between two "snapshots"
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* Location of a memory allocation: Python filename and line number
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The ``tracemalloc`` module is different than other third-party modules
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like ``Heapy`` or ``PySizer``, because it is focused on the location of
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a memory allocation rather that the object type or object content.
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API
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===
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To trace the most Python memory allocations, the module should be
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enabled as early as possible in your application by calling
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``tracemalloc.enable()`` function, by setting the ``PYTHONTRACEMALLOC``
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@ -36,200 +44,213 @@ environment variable to ``1``, or by using ``-X tracemalloc`` command
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line option.
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API
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===
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Functions
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---------
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enable():
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Start tracing Python memory allocations.
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Start tracing Python memory allocations.
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disable():
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Stop tracing Python memory allocations and stop the timer started by
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``start_timer()``.
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Stop tracing Python memory allocations and stop the timer started by
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``start_timer()``.
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is_enabled():
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``True`` if the module is enabled, ``False`` otherwise.
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Get the status of the module: ``True`` if it is enabled, ``False``
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otherwise.
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get_object_trace(obj):
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Get the trace of a Python object *obj* as a namedtuple with 3 attributes:
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Get the trace of a Python object *obj* as a namedtuple with 3 attributes:
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- ``size``: size in bytes of the object
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- ``filename``: name of the Python script where the object was allocated
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- ``lineno``: line number where the object was allocated
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- ``size``: size in bytes of the object
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- ``filename``: name of the Python script where the object was allocated
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- ``lineno``: line number where the object was allocated
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Return ``None`` if tracemalloc did not save the location where the object
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was allocated, for example if tracemalloc was disabled.
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Return ``None`` if tracemalloc did not save the location where the object
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was allocated, for example if tracemalloc was disabled.
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get_process_memory():
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Get the memory usage of the current process as a meminfo namedtuple with
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two attributes:
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Get the memory usage of the current process as a meminfo namedtuple
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with two attributes:
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* ``rss``: Resident Set Size in bytes
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* ``vms``: size of the virtual memory in bytes
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* ``rss``: Resident Set Size in bytes
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* ``vms``: size of the virtual memory in bytes
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Return ``None`` if the platform is not supported.
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Return ``None`` if the platform is not supported.
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Use the ``psutil`` module if available.
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Use the ``psutil`` module if available.
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start_timer(delay: int, func: callable, args: tuple=(), kwargs: dict={}):
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Start a timer calling ``func(*args, **kwargs)`` every *delay*
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seconds.
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Start a timer calling ``func(*args, **kwargs)`` every *delay*
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seconds.
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The timer is based on the Python memory allocator, it is not real
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time. *func* is called after at least *delay* seconds, it is not
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called exactly after *delay* seconds if no Python memory allocation
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occurred.
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The timer is based on the Python memory allocator, it is not real
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time. *func* is called after at least *delay* seconds, it is not
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called exactly after *delay* seconds if no Python memory allocation
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occurred.
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If ``start_timer()`` is called twice, previous parameters are
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replaced. The timer has a resolution of 1 second.
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If ``start_timer()`` is called twice, previous parameters are
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replaced. The timer has a resolution of 1 second.
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`start_timer()`` is used by ``DisplayTop`` and ``TakeSnapshot``
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to run regulary a task.
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`start_timer()`` is used by ``DisplayTop`` and ``TakeSnapshot`` to
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run regulary a task.
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stop_timer():
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Stop the timer started by ``start_timer()``.
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Stop the timer started by ``start_timer()``.
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DisplayTop class
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----------------
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DisplayTop(count: int, file=sys.stdout) class:
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``DisplayTop(count: int, file=sys.stdout)`` class:
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Display the list of the N biggest memory allocations.
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Display the list of the N biggest memory allocations.
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display() method:
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``display()`` method:
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Display the top
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Display the top
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start(delay: int) method:
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``start(delay: int)`` method:
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Start a task using tracemalloc timer to display the top every delay seconds.
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Start a task using tracemalloc timer to display the top every delay seconds.
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stop() method:
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``stop()`` method:
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Stop the task started by the ``DisplayTop.start()`` method
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Stop the task started by the ``DisplayTop.start()`` method
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color attribute:
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``color`` attribute:
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Use color if True (bool, default: stream.isatty()).
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``display()`` uses colors if ``True`` (bool,
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default: ``stream.isatty()``).
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compare_with_previous attribute:
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``compare_with_previous`` attribute:
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If ``True``, compare with the previous top if ``True``. If ``False``,
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compare with the first one (bool, default: ``True``): .
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If ``True``, ``display()`` compares with the previous top if
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``True``. If ``False``, compare with the first one (bool, default:
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``True``): .
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filename_parts attribute:
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``filename_parts`` attribute:
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Number of displayed filename parts (int, default: ``3``).
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show_average attribute:
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``show_average`` attribute:
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If ``True``, show the average size of allocations (bool, default: ``True``).
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If ``True``, ``display()`` shows the average size of allocations
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(bool, default: ``True``).
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show_count attribute:
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``show_count`` attribute:
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If ``True``, show the number of allocations (bool, default: ``True``).
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If ``True``, ``display()`` shows the number of allocations (bool, default: ``True``).
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show_lineno attribute:
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``show_lineno`` attribute:
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If ``True``, use also the line number, not only the filename (bool, default:
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``True``). If ``False``, only show the filename.
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If ``True``, use also the line number, not only the filename (bool,
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default: ``True``). If ``False``, only show the filename.
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show_size attribute:
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``show_size`` attribute:
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if ``True``, show the size of allocations (bool, default: ``True``).
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If ``True``, ``display()`` shows the size of allocations (bool,
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default: ``True``).
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user_data_callback attribute:
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``user_data_callback`` attribute:
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Optional callback collecting user data (callable, default:
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``None``). See ``Snapshot.create()``.
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Optional callback collecting user data (callable, default:
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``None``). See ``Snapshot.create()``.
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Snapshot class
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--------------
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Snapshot() class:
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``Snapshot()`` class:
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Snapshot of Python memory allocations. Use ``TakeSnapshot`` to regulary
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take snapshots.
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Snapshot of Python memory allocations. Use ``TakeSnapshot`` to
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regulary take snapshots.
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create(user_data_callback=None) method:
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``create(user_data_callback=None)`` method:
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Take a snapshot. If user_data_callback is specified, it must be a callable
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object returning a list of (title: str, format: str, value: int). format
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must be "size". The list must always have the same length and the same order
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to be able to compute differences between values.
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Take a snapshot. If user_data_callback is specified, it must be a
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callable object returning a list of (title: str, format: str, value:
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int). format must be "size". The list must always have the same
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length and the same order to be able to compute differences between
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values.
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Example: ``[('Video memory', 'size', 234902)]``.
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Example: ``[('Video memory', 'size', 234902)]``.
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filter_filenames(patterns: str|list, include: bool) method:
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``filter_filenames(patterns: str|list, include: bool)`` method:
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Remove filenames not matching any pattern if include is True, or remove
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filenames matching a pattern if include is False (exclude). See
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fnmatch.fnmatch() for the syntax of patterns.
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Remove filenames not matching any pattern if include is True, or
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remove filenames matching a pattern if include is False (exclude).
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See fnmatch.fnmatch() for the syntax of patterns.
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write(filename) method:
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``write(filename)`` method:
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Write the snapshot into a file.
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Write the snapshot into a file.
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load(filename), classmethod:
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``load(filename)`` classmethod:
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Load a snapshot from a file.
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Load a snapshot from a file.
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pid attribute:
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``process_memory`` attribute:
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Identifier of the process which created the snapshot (int).
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Memory usage of the process, result of ``get_process_memory()``.
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It can be ``None``.
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stats attribute:
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``user_data`` attribute:
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Raw memory allocation statistics (dict).
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Optional list of user data, result of *user_data_callback* in
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``Snapshot.create()`` (default: None).
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timestamp attribute:
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``pid`` attribute:
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Date and time of the creation of the snapshot (str).
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Identifier of the process which created the snapshot (int).
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``stats`` attribute:
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Raw memory allocation statistics (dict).
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``timestamp`` attribute:
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Date and time of the creation of the snapshot (str).
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TakeSnapshot class
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------------------
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TakeSnapshot class:
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``TakeSnapshot`` class:
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Task taking snapshots of Python memory allocations: write them into files.
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Task taking snapshots of Python memory allocations: write them into files.
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start(delay: int) method:
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``start(delay: int)`` method:
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Start a task taking a snapshot every delay seconds.
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Start a task taking a snapshot every delay seconds.
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stop() method:
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``stop()`` method:
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Stop the task started by the ``TakeSnapshot.start()`` method.
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Stop the task started by the ``TakeSnapshot.start()`` method.
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take_snapshot() method:
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``take_snapshot()`` method:
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Take a snapshot.
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Take a snapshot.
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filename_template attribute:
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``filename_template`` attribute:
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Template (str) to create a filename. "Variables" can be used in the
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template:
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Template (str) to create a filename. "Variables" can be used in the
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template:
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* ``$pid``: identifier of the current process
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* ``$timestamp``: current date and time
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* ``$counter``: counter starting at 1 and incremented at each snapshot
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* ``$pid``: identifier of the current process
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* ``$timestamp``: current date and time
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* ``$counter``: counter starting at 1 and incremented at each snapshot
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user_data_callback attribute:
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``user_data_callback`` attribute:
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Optional callback collecting user data (callable, default: None).
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See ``Snapshot.create()``.
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Optional callback collecting user data (callable, default: None).
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See ``Snapshot.create()``.
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Links
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