mirror of https://github.com/python/cpython
111 lines
3.6 KiB
ReStructuredText
111 lines
3.6 KiB
ReStructuredText
:mod:`pickletools` --- Tools for pickle developers
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==================================================
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.. module:: pickletools
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:synopsis: Contains extensive comments about the pickle protocols and
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pickle-machine opcodes, as well as some useful functions.
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**Source code:** :source:`Lib/pickletools.py`
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--------------
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This module contains various constants relating to the intimate details of the
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:mod:`pickle` module, some lengthy comments about the implementation, and a
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few useful functions for analyzing pickled data. The contents of this module
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are useful for Python core developers who are working on the :mod:`pickle`;
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ordinary users of the :mod:`pickle` module probably won't find the
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:mod:`pickletools` module relevant.
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Command line usage
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------------------
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.. versionadded:: 3.2
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When invoked from the command line, ``python -m pickletools`` will
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disassemble the contents of one or more pickle files. Note that if
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you want to see the Python object stored in the pickle rather than the
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details of pickle format, you may want to use ``-m pickle`` instead.
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However, when the pickle file that you want to examine comes from an
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untrusted source, ``-m pickletools`` is a safer option because it does
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not execute pickle bytecode.
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For example, with a tuple ``(1, 2)`` pickled in file ``x.pickle``:
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.. code-block:: shell-session
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$ python -m pickle x.pickle
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(1, 2)
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$ python -m pickletools x.pickle
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0: \x80 PROTO 3
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2: K BININT1 1
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4: K BININT1 2
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6: \x86 TUPLE2
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7: q BINPUT 0
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9: . STOP
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highest protocol among opcodes = 2
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Command line options
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^^^^^^^^^^^^^^^^^^^^
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.. program:: pickletools
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.. cmdoption:: -a, --annotate
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Annotate each line with a short opcode description.
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.. cmdoption:: -o, --output=<file>
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Name of a file where the output should be written.
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.. cmdoption:: -l, --indentlevel=<num>
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The number of blanks by which to indent a new MARK level.
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.. cmdoption:: -m, --memo
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When multiple objects are disassembled, preserve memo between
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disassemblies.
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.. cmdoption:: -p, --preamble=<preamble>
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When more than one pickle file are specified, print given preamble
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before each disassembly.
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Programmatic Interface
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----------------------
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.. function:: dis(pickle, out=None, memo=None, indentlevel=4, annotate=0)
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Outputs a symbolic disassembly of the pickle to the file-like
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object *out*, defaulting to ``sys.stdout``. *pickle* can be a
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string or a file-like object. *memo* can be a Python dictionary
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that will be used as the pickle's memo; it can be used to perform
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disassemblies across multiple pickles created by the same
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pickler. Successive levels, indicated by ``MARK`` opcodes in the
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stream, are indented by *indentlevel* spaces. If a nonzero value
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is given to *annotate*, each opcode in the output is annotated with
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a short description. The value of *annotate* is used as a hint for
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the column where annotation should start.
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.. versionadded:: 3.2
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The *annotate* argument.
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.. function:: genops(pickle)
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Provides an :term:`iterator` over all of the opcodes in a pickle, returning a
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sequence of ``(opcode, arg, pos)`` triples. *opcode* is an instance of an
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:class:`OpcodeInfo` class; *arg* is the decoded value, as a Python object, of
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the opcode's argument; *pos* is the position at which this opcode is located.
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*pickle* can be a string or a file-like object.
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.. function:: optimize(picklestring)
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Returns a new equivalent pickle string after eliminating unused ``PUT``
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opcodes. The optimized pickle is shorter, takes less transmission time,
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requires less storage space, and unpickles more efficiently.
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