mirror of https://github.com/python/cpython
766 lines
25 KiB
ReStructuredText
766 lines
25 KiB
ReStructuredText
:mod:`tracemalloc` --- Trace memory allocations
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===============================================
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.. module:: tracemalloc
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:synopsis: Trace memory allocations.
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.. versionadded:: 3.4
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**Source code:** :source:`Lib/tracemalloc.py`
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--------------
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The tracemalloc module is a debug tool to trace memory blocks allocated by
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Python. It provides the following information:
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* Traceback where an object was allocated
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* Statistics on allocated memory blocks per filename and per line number:
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total size, number and average size of allocated memory blocks
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* Compute the differences between two snapshots to detect memory leaks
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To trace most memory blocks allocated by Python, the module should be started
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as early as possible by setting the :envvar:`PYTHONTRACEMALLOC` environment
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variable to ``1``, or by using :option:`-X` ``tracemalloc`` command line
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option. The :func:`tracemalloc.start` function can be called at runtime to
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start tracing Python memory allocations.
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By default, a trace of an allocated memory block only stores the most recent
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frame (1 frame). To store 25 frames at startup: set the
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:envvar:`PYTHONTRACEMALLOC` environment variable to ``25``, or use the
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:option:`-X` ``tracemalloc=25`` command line option.
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Examples
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--------
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Display the top 10
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^^^^^^^^^^^^^^^^^^
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Display the 10 files allocating the most memory::
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import tracemalloc
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tracemalloc.start()
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# ... run your application ...
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snapshot = tracemalloc.take_snapshot()
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top_stats = snapshot.statistics('lineno')
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print("[ Top 10 ]")
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for stat in top_stats[:10]:
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print(stat)
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Example of output of the Python test suite::
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[ Top 10 ]
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<frozen importlib._bootstrap>:716: size=4855 KiB, count=39328, average=126 B
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<frozen importlib._bootstrap>:284: size=521 KiB, count=3199, average=167 B
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/usr/lib/python3.4/collections/__init__.py:368: size=244 KiB, count=2315, average=108 B
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/usr/lib/python3.4/unittest/case.py:381: size=185 KiB, count=779, average=243 B
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/usr/lib/python3.4/unittest/case.py:402: size=154 KiB, count=378, average=416 B
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/usr/lib/python3.4/abc.py:133: size=88.7 KiB, count=347, average=262 B
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<frozen importlib._bootstrap>:1446: size=70.4 KiB, count=911, average=79 B
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<frozen importlib._bootstrap>:1454: size=52.0 KiB, count=25, average=2131 B
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<string>:5: size=49.7 KiB, count=148, average=344 B
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/usr/lib/python3.4/sysconfig.py:411: size=48.0 KiB, count=1, average=48.0 KiB
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We can see that Python loaded ``4855 KiB`` data (bytecode and constants) from
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modules and that the :mod:`collections` module allocated ``244 KiB`` to build
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:class:`~collections.namedtuple` types.
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See :meth:`Snapshot.statistics` for more options.
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Compute differences
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^^^^^^^^^^^^^^^^^^^
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Take two snapshots and display the differences::
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import tracemalloc
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tracemalloc.start()
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# ... start your application ...
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snapshot1 = tracemalloc.take_snapshot()
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# ... call the function leaking memory ...
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snapshot2 = tracemalloc.take_snapshot()
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top_stats = snapshot2.compare_to(snapshot1, 'lineno')
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print("[ Top 10 differences ]")
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for stat in top_stats[:10]:
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print(stat)
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Example of output before/after running some tests of the Python test suite::
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[ Top 10 differences ]
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<frozen importlib._bootstrap>:716: size=8173 KiB (+4428 KiB), count=71332 (+39369), average=117 B
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/usr/lib/python3.4/linecache.py:127: size=940 KiB (+940 KiB), count=8106 (+8106), average=119 B
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/usr/lib/python3.4/unittest/case.py:571: size=298 KiB (+298 KiB), count=589 (+589), average=519 B
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<frozen importlib._bootstrap>:284: size=1005 KiB (+166 KiB), count=7423 (+1526), average=139 B
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/usr/lib/python3.4/mimetypes.py:217: size=112 KiB (+112 KiB), count=1334 (+1334), average=86 B
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/usr/lib/python3.4/http/server.py:848: size=96.0 KiB (+96.0 KiB), count=1 (+1), average=96.0 KiB
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/usr/lib/python3.4/inspect.py:1465: size=83.5 KiB (+83.5 KiB), count=109 (+109), average=784 B
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/usr/lib/python3.4/unittest/mock.py:491: size=77.7 KiB (+77.7 KiB), count=143 (+143), average=557 B
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/usr/lib/python3.4/urllib/parse.py:476: size=71.8 KiB (+71.8 KiB), count=969 (+969), average=76 B
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/usr/lib/python3.4/contextlib.py:38: size=67.2 KiB (+67.2 KiB), count=126 (+126), average=546 B
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We can see that Python has loaded ``8173 KiB`` of module data (bytecode and
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constants), and that this is ``4428 KiB`` more than had been loaded before the
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tests, when the previous snapshot was taken. Similarly, the :mod:`linecache`
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module has cached ``940 KiB`` of Python source code to format tracebacks, all
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of it since the previous snapshot.
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If the system has little free memory, snapshots can be written on disk using
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the :meth:`Snapshot.dump` method to analyze the snapshot offline. Then use the
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:meth:`Snapshot.load` method reload the snapshot.
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Get the traceback of a memory block
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Code to display the traceback of the biggest memory block::
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import tracemalloc
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# Store 25 frames
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tracemalloc.start(25)
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# ... run your application ...
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snapshot = tracemalloc.take_snapshot()
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top_stats = snapshot.statistics('traceback')
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# pick the biggest memory block
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stat = top_stats[0]
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print("%s memory blocks: %.1f KiB" % (stat.count, stat.size / 1024))
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for line in stat.traceback.format():
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print(line)
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Example of output of the Python test suite (traceback limited to 25 frames)::
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903 memory blocks: 870.1 KiB
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File "<frozen importlib._bootstrap>", line 716
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File "<frozen importlib._bootstrap>", line 1036
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File "<frozen importlib._bootstrap>", line 934
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File "<frozen importlib._bootstrap>", line 1068
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File "<frozen importlib._bootstrap>", line 619
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File "<frozen importlib._bootstrap>", line 1581
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File "<frozen importlib._bootstrap>", line 1614
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File "/usr/lib/python3.4/doctest.py", line 101
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import pdb
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File "<frozen importlib._bootstrap>", line 284
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File "<frozen importlib._bootstrap>", line 938
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File "<frozen importlib._bootstrap>", line 1068
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File "<frozen importlib._bootstrap>", line 619
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File "<frozen importlib._bootstrap>", line 1581
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File "<frozen importlib._bootstrap>", line 1614
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File "/usr/lib/python3.4/test/support/__init__.py", line 1728
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import doctest
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File "/usr/lib/python3.4/test/test_pickletools.py", line 21
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support.run_doctest(pickletools)
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File "/usr/lib/python3.4/test/regrtest.py", line 1276
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test_runner()
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File "/usr/lib/python3.4/test/regrtest.py", line 976
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display_failure=not verbose)
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File "/usr/lib/python3.4/test/regrtest.py", line 761
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match_tests=ns.match_tests)
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File "/usr/lib/python3.4/test/regrtest.py", line 1563
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main()
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File "/usr/lib/python3.4/test/__main__.py", line 3
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regrtest.main_in_temp_cwd()
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File "/usr/lib/python3.4/runpy.py", line 73
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exec(code, run_globals)
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File "/usr/lib/python3.4/runpy.py", line 160
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"__main__", fname, loader, pkg_name)
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We can see that the most memory was allocated in the :mod:`importlib` module to
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load data (bytecode and constants) from modules: ``870.1 KiB``. The traceback is
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where the :mod:`importlib` loaded data most recently: on the ``import pdb``
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line of the :mod:`doctest` module. The traceback may change if a new module is
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loaded.
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Pretty top
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^^^^^^^^^^
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Code to display the 10 lines allocating the most memory with a pretty output,
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ignoring ``<frozen importlib._bootstrap>`` and ``<unknown>`` files::
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import linecache
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import os
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import tracemalloc
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def display_top(snapshot, key_type='lineno', limit=10):
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snapshot = snapshot.filter_traces((
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tracemalloc.Filter(False, "<frozen importlib._bootstrap>"),
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tracemalloc.Filter(False, "<unknown>"),
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))
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top_stats = snapshot.statistics(key_type)
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print("Top %s lines" % limit)
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for index, stat in enumerate(top_stats[:limit], 1):
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frame = stat.traceback[0]
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print("#%s: %s:%s: %.1f KiB"
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% (index, frame.filename, frame.lineno, stat.size / 1024))
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line = linecache.getline(frame.filename, frame.lineno).strip()
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if line:
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print(' %s' % line)
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other = top_stats[limit:]
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if other:
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size = sum(stat.size for stat in other)
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print("%s other: %.1f KiB" % (len(other), size / 1024))
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total = sum(stat.size for stat in top_stats)
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print("Total allocated size: %.1f KiB" % (total / 1024))
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tracemalloc.start()
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# ... run your application ...
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snapshot = tracemalloc.take_snapshot()
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display_top(snapshot)
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Example of output of the Python test suite::
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Top 10 lines
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#1: Lib/base64.py:414: 419.8 KiB
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_b85chars2 = [(a + b) for a in _b85chars for b in _b85chars]
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#2: Lib/base64.py:306: 419.8 KiB
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_a85chars2 = [(a + b) for a in _a85chars for b in _a85chars]
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#3: collections/__init__.py:368: 293.6 KiB
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exec(class_definition, namespace)
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#4: Lib/abc.py:133: 115.2 KiB
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cls = super().__new__(mcls, name, bases, namespace)
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#5: unittest/case.py:574: 103.1 KiB
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testMethod()
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#6: Lib/linecache.py:127: 95.4 KiB
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lines = fp.readlines()
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#7: urllib/parse.py:476: 71.8 KiB
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for a in _hexdig for b in _hexdig}
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#8: <string>:5: 62.0 KiB
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#9: Lib/_weakrefset.py:37: 60.0 KiB
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self.data = set()
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#10: Lib/base64.py:142: 59.8 KiB
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_b32tab2 = [a + b for a in _b32tab for b in _b32tab]
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6220 other: 3602.8 KiB
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Total allocated size: 5303.1 KiB
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See :meth:`Snapshot.statistics` for more options.
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Record the current and peak size of all traced memory blocks
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The following code computes two sums like ``0 + 1 + 2 + ...`` inefficiently, by
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creating a list of those numbers. This list consumes a lot of memory
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temporarily. We can use :func:`get_traced_memory` and :func:`reset_peak` to
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observe the small memory usage after the sum is computed as well as the peak
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memory usage during the computations::
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import tracemalloc
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tracemalloc.start()
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# Example code: compute a sum with a large temporary list
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large_sum = sum(list(range(100000)))
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first_size, first_peak = tracemalloc.get_traced_memory()
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tracemalloc.reset_peak()
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# Example code: compute a sum with a small temporary list
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small_sum = sum(list(range(1000)))
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second_size, second_peak = tracemalloc.get_traced_memory()
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print(f"{first_size=}, {first_peak=}")
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print(f"{second_size=}, {second_peak=}")
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Output::
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first_size=664, first_peak=3592984
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second_size=804, second_peak=29704
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Using :func:`reset_peak` ensured we could accurately record the peak during the
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computation of ``small_sum``, even though it is much smaller than the overall
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peak size of memory blocks since the :func:`start` call. Without the call to
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:func:`reset_peak`, ``second_peak`` would still be the peak from the
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computation ``large_sum`` (that is, equal to ``first_peak``). In this case,
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both peaks are much higher than the final memory usage, and which suggests we
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could optimise (by removing the unnecessary call to :class:`list`, and writing
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``sum(range(...))``).
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API
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---
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Functions
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^^^^^^^^^
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.. function:: clear_traces()
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Clear traces of memory blocks allocated by Python.
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See also :func:`stop`.
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.. function:: get_object_traceback(obj)
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Get the traceback where the Python object *obj* was allocated.
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Return a :class:`Traceback` instance, or ``None`` if the :mod:`tracemalloc`
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module is not tracing memory allocations or did not trace the allocation of
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the object.
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See also :func:`gc.get_referrers` and :func:`sys.getsizeof` functions.
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.. function:: get_traceback_limit()
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Get the maximum number of frames stored in the traceback of a trace.
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The :mod:`tracemalloc` module must be tracing memory allocations to
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get the limit, otherwise an exception is raised.
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The limit is set by the :func:`start` function.
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.. function:: get_traced_memory()
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Get the current size and peak size of memory blocks traced by the
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:mod:`tracemalloc` module as a tuple: ``(current: int, peak: int)``.
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.. function:: reset_peak()
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Set the peak size of memory blocks traced by the :mod:`tracemalloc` module
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to the current size.
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Do nothing if the :mod:`tracemalloc` module is not tracing memory
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allocations.
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This function only modifies the recorded peak size, and does not modify or
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clear any traces, unlike :func:`clear_traces`. Snapshots taken with
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:func:`take_snapshot` before a call to :func:`reset_peak` can be
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meaningfully compared to snapshots taken after the call.
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See also :func:`get_traced_memory`.
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.. versionadded:: 3.9
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.. function:: get_tracemalloc_memory()
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Get the memory usage in bytes of the :mod:`tracemalloc` module used to store
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traces of memory blocks.
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Return an :class:`int`.
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.. function:: is_tracing()
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``True`` if the :mod:`tracemalloc` module is tracing Python memory
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allocations, ``False`` otherwise.
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See also :func:`start` and :func:`stop` functions.
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.. function:: start(nframe: int=1)
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Start tracing Python memory allocations: install hooks on Python memory
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allocators. Collected tracebacks of traces will be limited to *nframe*
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frames. By default, a trace of a memory block only stores the most recent
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frame: the limit is ``1``. *nframe* must be greater or equal to ``1``.
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You can still read the original number of total frames that composed the
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traceback by looking at the :attr:`Traceback.total_nframe` attribute.
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Storing more than ``1`` frame is only useful to compute statistics grouped
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by ``'traceback'`` or to compute cumulative statistics: see the
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:meth:`Snapshot.compare_to` and :meth:`Snapshot.statistics` methods.
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Storing more frames increases the memory and CPU overhead of the
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:mod:`tracemalloc` module. Use the :func:`get_tracemalloc_memory` function
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to measure how much memory is used by the :mod:`tracemalloc` module.
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The :envvar:`PYTHONTRACEMALLOC` environment variable
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(``PYTHONTRACEMALLOC=NFRAME``) and the :option:`-X` ``tracemalloc=NFRAME``
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command line option can be used to start tracing at startup.
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See also :func:`stop`, :func:`is_tracing` and :func:`get_traceback_limit`
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functions.
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.. function:: stop()
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Stop tracing Python memory allocations: uninstall hooks on Python memory
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allocators. Also clears all previously collected traces of memory blocks
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allocated by Python.
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Call :func:`take_snapshot` function to take a snapshot of traces before
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clearing them.
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See also :func:`start`, :func:`is_tracing` and :func:`clear_traces`
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functions.
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.. function:: take_snapshot()
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Take a snapshot of traces of memory blocks allocated by Python. Return a new
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:class:`Snapshot` instance.
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The snapshot does not include memory blocks allocated before the
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:mod:`tracemalloc` module started to trace memory allocations.
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Tracebacks of traces are limited to :func:`get_traceback_limit` frames. Use
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the *nframe* parameter of the :func:`start` function to store more frames.
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The :mod:`tracemalloc` module must be tracing memory allocations to take a
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snapshot, see the :func:`start` function.
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See also the :func:`get_object_traceback` function.
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DomainFilter
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^^^^^^^^^^^^
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.. class:: DomainFilter(inclusive: bool, domain: int)
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Filter traces of memory blocks by their address space (domain).
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.. versionadded:: 3.6
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.. attribute:: inclusive
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If *inclusive* is ``True`` (include), match memory blocks allocated
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in the address space :attr:`domain`.
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If *inclusive* is ``False`` (exclude), match memory blocks not allocated
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in the address space :attr:`domain`.
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.. attribute:: domain
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Address space of a memory block (``int``). Read-only property.
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Filter
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^^^^^^
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.. class:: Filter(inclusive: bool, filename_pattern: str, lineno: int=None, all_frames: bool=False, domain: int=None)
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Filter on traces of memory blocks.
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See the :func:`fnmatch.fnmatch` function for the syntax of
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*filename_pattern*. The ``'.pyc'`` file extension is
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replaced with ``'.py'``.
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Examples:
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* ``Filter(True, subprocess.__file__)`` only includes traces of the
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:mod:`subprocess` module
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* ``Filter(False, tracemalloc.__file__)`` excludes traces of the
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:mod:`tracemalloc` module
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* ``Filter(False, "<unknown>")`` excludes empty tracebacks
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.. versionchanged:: 3.5
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The ``'.pyo'`` file extension is no longer replaced with ``'.py'``.
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.. versionchanged:: 3.6
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Added the :attr:`domain` attribute.
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.. attribute:: domain
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Address space of a memory block (``int`` or ``None``).
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tracemalloc uses the domain ``0`` to trace memory allocations made by
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Python. C extensions can use other domains to trace other resources.
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.. attribute:: inclusive
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If *inclusive* is ``True`` (include), only match memory blocks allocated
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in a file with a name matching :attr:`filename_pattern` at line number
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:attr:`lineno`.
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If *inclusive* is ``False`` (exclude), ignore memory blocks allocated in
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a file with a name matching :attr:`filename_pattern` at line number
|
|
:attr:`lineno`.
|
|
|
|
.. attribute:: lineno
|
|
|
|
Line number (``int``) of the filter. If *lineno* is ``None``, the filter
|
|
matches any line number.
|
|
|
|
.. attribute:: filename_pattern
|
|
|
|
Filename pattern of the filter (``str``). Read-only property.
|
|
|
|
.. attribute:: all_frames
|
|
|
|
If *all_frames* is ``True``, all frames of the traceback are checked. If
|
|
*all_frames* is ``False``, only the most recent frame is checked.
|
|
|
|
This attribute has no effect if the traceback limit is ``1``. See the
|
|
:func:`get_traceback_limit` function and :attr:`Snapshot.traceback_limit`
|
|
attribute.
|
|
|
|
|
|
Frame
|
|
^^^^^
|
|
|
|
.. class:: Frame
|
|
|
|
Frame of a traceback.
|
|
|
|
The :class:`Traceback` class is a sequence of :class:`Frame` instances.
|
|
|
|
.. attribute:: filename
|
|
|
|
Filename (``str``).
|
|
|
|
.. attribute:: lineno
|
|
|
|
Line number (``int``).
|
|
|
|
|
|
Snapshot
|
|
^^^^^^^^
|
|
|
|
.. class:: Snapshot
|
|
|
|
Snapshot of traces of memory blocks allocated by Python.
|
|
|
|
The :func:`take_snapshot` function creates a snapshot instance.
|
|
|
|
.. method:: compare_to(old_snapshot: Snapshot, key_type: str, cumulative: bool=False)
|
|
|
|
Compute the differences with an old snapshot. Get statistics as a sorted
|
|
list of :class:`StatisticDiff` instances grouped by *key_type*.
|
|
|
|
See the :meth:`Snapshot.statistics` method for *key_type* and *cumulative*
|
|
parameters.
|
|
|
|
The result is sorted from the biggest to the smallest by: absolute value
|
|
of :attr:`StatisticDiff.size_diff`, :attr:`StatisticDiff.size`, absolute
|
|
value of :attr:`StatisticDiff.count_diff`, :attr:`Statistic.count` and
|
|
then by :attr:`StatisticDiff.traceback`.
|
|
|
|
|
|
.. method:: dump(filename)
|
|
|
|
Write the snapshot into a file.
|
|
|
|
Use :meth:`load` to reload the snapshot.
|
|
|
|
|
|
.. method:: filter_traces(filters)
|
|
|
|
Create a new :class:`Snapshot` instance with a filtered :attr:`traces`
|
|
sequence, *filters* is a list of :class:`DomainFilter` and
|
|
:class:`Filter` instances. If *filters* is an empty list, return a new
|
|
:class:`Snapshot` instance with a copy of the traces.
|
|
|
|
All inclusive filters are applied at once, a trace is ignored if no
|
|
inclusive filters match it. A trace is ignored if at least one exclusive
|
|
filter matches it.
|
|
|
|
.. versionchanged:: 3.6
|
|
:class:`DomainFilter` instances are now also accepted in *filters*.
|
|
|
|
|
|
.. classmethod:: load(filename)
|
|
|
|
Load a snapshot from a file.
|
|
|
|
See also :meth:`dump`.
|
|
|
|
|
|
.. method:: statistics(key_type: str, cumulative: bool=False)
|
|
|
|
Get statistics as a sorted list of :class:`Statistic` instances grouped
|
|
by *key_type*:
|
|
|
|
===================== ========================
|
|
key_type description
|
|
===================== ========================
|
|
``'filename'`` filename
|
|
``'lineno'`` filename and line number
|
|
``'traceback'`` traceback
|
|
===================== ========================
|
|
|
|
If *cumulative* is ``True``, cumulate size and count of memory blocks of
|
|
all frames of the traceback of a trace, not only the most recent frame.
|
|
The cumulative mode can only be used with *key_type* equals to
|
|
``'filename'`` and ``'lineno'``.
|
|
|
|
The result is sorted from the biggest to the smallest by:
|
|
:attr:`Statistic.size`, :attr:`Statistic.count` and then by
|
|
:attr:`Statistic.traceback`.
|
|
|
|
|
|
.. attribute:: traceback_limit
|
|
|
|
Maximum number of frames stored in the traceback of :attr:`traces`:
|
|
result of the :func:`get_traceback_limit` when the snapshot was taken.
|
|
|
|
.. attribute:: traces
|
|
|
|
Traces of all memory blocks allocated by Python: sequence of
|
|
:class:`Trace` instances.
|
|
|
|
The sequence has an undefined order. Use the :meth:`Snapshot.statistics`
|
|
method to get a sorted list of statistics.
|
|
|
|
|
|
Statistic
|
|
^^^^^^^^^
|
|
|
|
.. class:: Statistic
|
|
|
|
Statistic on memory allocations.
|
|
|
|
:func:`Snapshot.statistics` returns a list of :class:`Statistic` instances.
|
|
|
|
See also the :class:`StatisticDiff` class.
|
|
|
|
.. attribute:: count
|
|
|
|
Number of memory blocks (``int``).
|
|
|
|
.. attribute:: size
|
|
|
|
Total size of memory blocks in bytes (``int``).
|
|
|
|
.. attribute:: traceback
|
|
|
|
Traceback where the memory block was allocated, :class:`Traceback`
|
|
instance.
|
|
|
|
|
|
StatisticDiff
|
|
^^^^^^^^^^^^^
|
|
|
|
.. class:: StatisticDiff
|
|
|
|
Statistic difference on memory allocations between an old and a new
|
|
:class:`Snapshot` instance.
|
|
|
|
:func:`Snapshot.compare_to` returns a list of :class:`StatisticDiff`
|
|
instances. See also the :class:`Statistic` class.
|
|
|
|
.. attribute:: count
|
|
|
|
Number of memory blocks in the new snapshot (``int``): ``0`` if
|
|
the memory blocks have been released in the new snapshot.
|
|
|
|
.. attribute:: count_diff
|
|
|
|
Difference of number of memory blocks between the old and the new
|
|
snapshots (``int``): ``0`` if the memory blocks have been allocated in
|
|
the new snapshot.
|
|
|
|
.. attribute:: size
|
|
|
|
Total size of memory blocks in bytes in the new snapshot (``int``):
|
|
``0`` if the memory blocks have been released in the new snapshot.
|
|
|
|
.. attribute:: size_diff
|
|
|
|
Difference of total size of memory blocks in bytes between the old and
|
|
the new snapshots (``int``): ``0`` if the memory blocks have been
|
|
allocated in the new snapshot.
|
|
|
|
.. attribute:: traceback
|
|
|
|
Traceback where the memory blocks were allocated, :class:`Traceback`
|
|
instance.
|
|
|
|
|
|
Trace
|
|
^^^^^
|
|
|
|
.. class:: Trace
|
|
|
|
Trace of a memory block.
|
|
|
|
The :attr:`Snapshot.traces` attribute is a sequence of :class:`Trace`
|
|
instances.
|
|
|
|
.. versionchanged:: 3.6
|
|
Added the :attr:`domain` attribute.
|
|
|
|
.. attribute:: domain
|
|
|
|
Address space of a memory block (``int``). Read-only property.
|
|
|
|
tracemalloc uses the domain ``0`` to trace memory allocations made by
|
|
Python. C extensions can use other domains to trace other resources.
|
|
|
|
.. attribute:: size
|
|
|
|
Size of the memory block in bytes (``int``).
|
|
|
|
.. attribute:: traceback
|
|
|
|
Traceback where the memory block was allocated, :class:`Traceback`
|
|
instance.
|
|
|
|
|
|
Traceback
|
|
^^^^^^^^^
|
|
|
|
.. class:: Traceback
|
|
|
|
Sequence of :class:`Frame` instances sorted from the oldest frame to the
|
|
most recent frame.
|
|
|
|
A traceback contains at least ``1`` frame. If the ``tracemalloc`` module
|
|
failed to get a frame, the filename ``"<unknown>"`` at line number ``0`` is
|
|
used.
|
|
|
|
When a snapshot is taken, tracebacks of traces are limited to
|
|
:func:`get_traceback_limit` frames. See the :func:`take_snapshot` function.
|
|
The original number of frames of the traceback is stored in the
|
|
:attr:`Traceback.total_nframe` attribute. That allows to know if a traceback
|
|
has been truncated by the traceback limit.
|
|
|
|
The :attr:`Trace.traceback` attribute is an instance of :class:`Traceback`
|
|
instance.
|
|
|
|
.. versionchanged:: 3.7
|
|
Frames are now sorted from the oldest to the most recent, instead of most recent to oldest.
|
|
|
|
.. attribute:: total_nframe
|
|
|
|
Total number of frames that composed the traceback before truncation.
|
|
This attribute can be set to ``None`` if the information is not
|
|
available.
|
|
|
|
.. versionchanged:: 3.9
|
|
The :attr:`Traceback.total_nframe` attribute was added.
|
|
|
|
.. method:: format(limit=None, most_recent_first=False)
|
|
|
|
Format the traceback as a list of lines. Use the :mod:`linecache` module to
|
|
retrieve lines from the source code. If *limit* is set, format the *limit*
|
|
most recent frames if *limit* is positive. Otherwise, format the
|
|
``abs(limit)`` oldest frames. If *most_recent_first* is ``True``, the order
|
|
of the formatted frames is reversed, returning the most recent frame first
|
|
instead of last.
|
|
|
|
Similar to the :func:`traceback.format_tb` function, except that
|
|
:meth:`.format` does not include newlines.
|
|
|
|
Example::
|
|
|
|
print("Traceback (most recent call first):")
|
|
for line in traceback:
|
|
print(line)
|
|
|
|
Output::
|
|
|
|
Traceback (most recent call first):
|
|
File "test.py", line 9
|
|
obj = Object()
|
|
File "test.py", line 12
|
|
tb = tracemalloc.get_object_traceback(f())
|