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Python now supports checking bytecode cache up-to-dateness with a hash of the source contents rather than volatile source metadata. See the PEP for details. While a fairly straightforward idea, quite a lot of code had to be modified due to the pervasiveness of pyc implementation details in the codebase. Changes in this commit include: - The core changes to importlib to understand how to read, validate, and regenerate hash-based pycs. - Support for generating hash-based pycs in py_compile and compileall. - Modifications to our siphash implementation to support passing a custom key. We then expose it to importlib through _imp. - Updates to all places in the interpreter, standard library, and tests that manually generate or parse pyc files to grok the new format. - Support in the interpreter command line code for long options like --check-hash-based-pycs. - Tests and documentation for all of the above.
129 lines
5.3 KiB
ReStructuredText
129 lines
5.3 KiB
ReStructuredText
:mod:`py_compile` --- Compile Python source files
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=================================================
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.. module:: py_compile
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:synopsis: Generate byte-code files from Python source files.
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.. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org>
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.. documentation based on module docstrings
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**Source code:** :source:`Lib/py_compile.py`
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.. index:: pair: file; byte-code
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--------------
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The :mod:`py_compile` module provides a function to generate a byte-code file
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from a source file, and another function used when the module source file is
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invoked as a script.
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Though not often needed, this function can be useful when installing modules for
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shared use, especially if some of the users may not have permission to write the
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byte-code cache files in the directory containing the source code.
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.. exception:: PyCompileError
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Exception raised when an error occurs while attempting to compile the file.
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.. function:: compile(file, cfile=None, dfile=None, doraise=False, optimize=-1, invalidation_mode=PycInvalidationMode.TIMESTAMP)
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Compile a source file to byte-code and write out the byte-code cache file.
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The source code is loaded from the file named *file*. The byte-code is
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written to *cfile*, which defaults to the :pep:`3147`/:pep:`488` path, ending
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in ``.pyc``.
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For example, if *file* is ``/foo/bar/baz.py`` *cfile* will default to
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``/foo/bar/__pycache__/baz.cpython-32.pyc`` for Python 3.2. If *dfile* is
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specified, it is used as the name of the source file in error messages when
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instead of *file*. If *doraise* is true, a :exc:`PyCompileError` is raised
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when an error is encountered while compiling *file*. If *doraise* is false
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(the default), an error string is written to ``sys.stderr``, but no exception
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is raised. This function returns the path to byte-compiled file, i.e.
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whatever *cfile* value was used.
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If the path that *cfile* becomes (either explicitly specified or computed)
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is a symlink or non-regular file, :exc:`FileExistsError` will be raised.
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This is to act as a warning that import will turn those paths into regular
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files if it is allowed to write byte-compiled files to those paths. This is
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a side-effect of import using file renaming to place the final byte-compiled
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file into place to prevent concurrent file writing issues.
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*optimize* controls the optimization level and is passed to the built-in
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:func:`compile` function. The default of ``-1`` selects the optimization
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level of the current interpreter.
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*invalidation_mode* should be a member of the :class:`PycInvalidationMode`
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enum and controls how the generated ``.pyc`` files are invalidated at
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runtime.
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.. versionchanged:: 3.2
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Changed default value of *cfile* to be :PEP:`3147`-compliant. Previous
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default was *file* + ``'c'`` (``'o'`` if optimization was enabled).
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Also added the *optimize* parameter.
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.. versionchanged:: 3.4
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Changed code to use :mod:`importlib` for the byte-code cache file writing.
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This means file creation/writing semantics now match what :mod:`importlib`
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does, e.g. permissions, write-and-move semantics, etc. Also added the
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caveat that :exc:`FileExistsError` is raised if *cfile* is a symlink or
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non-regular file.
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.. versionchanged:: 3.7
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The *invalidation_mode* parameter was added as specified in :pep:`552`.
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.. class:: PycInvalidationMode
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A enumeration of possible methods the interpreter can use to determine
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whether a bytecode file is up to date with a source file. The ``.pyc`` file
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indicates the desired invalidation mode in its header. See
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:ref:`pyc-invalidation` for more information on how Python invalidates
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``.pyc`` files at runtime.
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.. versionadded:: 3.7
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.. attribute:: TIMESTAMP
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The ``.pyc`` file includes the timestamp and size of the source file,
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which Python will compare against the metadata of the source file at
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runtime to determine if the ``.pyc`` file needs to be regenerated.
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.. attribute:: CHECKED_HASH
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The ``.pyc`` file includes a hash of the source file content, which Python
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will compare against the source at runtime to determine if the ``.pyc``
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file needs to be regenerated.
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.. attribute:: UNCHECKED_HASH
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Like :attr:`CHECKED_HASH`, the ``.pyc`` file includes a hash of the source
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file content. However, Python will at runtime assume the ``.pyc`` file is
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up to date and not validate the ``.pyc`` against the source file at all.
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This option is useful when the ``.pycs`` are kept up to date by some
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system external to Python like a build system.
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.. function:: main(args=None)
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Compile several source files. The files named in *args* (or on the command
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line, if *args* is ``None``) are compiled and the resulting byte-code is
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cached in the normal manner. This function does not search a directory
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structure to locate source files; it only compiles files named explicitly.
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If ``'-'`` is the only parameter in args, the list of files is taken from
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standard input.
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.. versionchanged:: 3.2
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Added support for ``'-'``.
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When this module is run as a script, the :func:`main` is used to compile all the
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files named on the command line. The exit status is nonzero if one of the files
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could not be compiled.
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.. seealso::
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Module :mod:`compileall`
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Utilities to compile all Python source files in a directory tree.
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