1:mod:`py_compile` --- Compile Python source files 2================================================= 3 4.. module:: py_compile 5 :synopsis: Generate byte-code files from Python source files. 6 7.. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org> 8.. documentation based on module docstrings 9 10**Source code:** :source:`Lib/py_compile.py` 11 12.. index:: pair: file; byte-code 13 14-------------- 15 16The :mod:`py_compile` module provides a function to generate a byte-code file 17from a source file, and another function used when the module source file is 18invoked as a script. 19 20Though not often needed, this function can be useful when installing modules for 21shared use, especially if some of the users may not have permission to write the 22byte-code cache files in the directory containing the source code. 23 24 25.. exception:: PyCompileError 26 27 Exception raised when an error occurs while attempting to compile the file. 28 29 30.. function:: compile(file, cfile=None, dfile=None, doraise=False, optimize=-1, invalidation_mode=PycInvalidationMode.TIMESTAMP) 31 32 Compile a source file to byte-code and write out the byte-code cache file. 33 The source code is loaded from the file named *file*. The byte-code is 34 written to *cfile*, which defaults to the :pep:`3147`/:pep:`488` path, ending 35 in ``.pyc``. 36 For example, if *file* is ``/foo/bar/baz.py`` *cfile* will default to 37 ``/foo/bar/__pycache__/baz.cpython-32.pyc`` for Python 3.2. If *dfile* is 38 specified, it is used as the name of the source file in error messages when 39 instead of *file*. If *doraise* is true, a :exc:`PyCompileError` is raised 40 when an error is encountered while compiling *file*. If *doraise* is false 41 (the default), an error string is written to ``sys.stderr``, but no exception 42 is raised. This function returns the path to byte-compiled file, i.e. 43 whatever *cfile* value was used. 44 45 If the path that *cfile* becomes (either explicitly specified or computed) 46 is a symlink or non-regular file, :exc:`FileExistsError` will be raised. 47 This is to act as a warning that import will turn those paths into regular 48 files if it is allowed to write byte-compiled files to those paths. This is 49 a side-effect of import using file renaming to place the final byte-compiled 50 file into place to prevent concurrent file writing issues. 51 52 *optimize* controls the optimization level and is passed to the built-in 53 :func:`compile` function. The default of ``-1`` selects the optimization 54 level of the current interpreter. 55 56 *invalidation_mode* should be a member of the :class:`PycInvalidationMode` 57 enum and controls how the generated bytecode cache is invalidated at 58 runtime. The default is :attr:`PycInvalidationMode.CHECKED_HASH` if 59 the :envvar:`SOURCE_DATE_EPOCH` environment variable is set, otherwise 60 the default is :attr:`PycInvalidationMode.TIMESTAMP`. 61 62 .. versionchanged:: 3.2 63 Changed default value of *cfile* to be :PEP:`3147`-compliant. Previous 64 default was *file* + ``'c'`` (``'o'`` if optimization was enabled). 65 Also added the *optimize* parameter. 66 67 .. versionchanged:: 3.4 68 Changed code to use :mod:`importlib` for the byte-code cache file writing. 69 This means file creation/writing semantics now match what :mod:`importlib` 70 does, e.g. permissions, write-and-move semantics, etc. Also added the 71 caveat that :exc:`FileExistsError` is raised if *cfile* is a symlink or 72 non-regular file. 73 74 .. versionchanged:: 3.7 75 The *invalidation_mode* parameter was added as specified in :pep:`552`. 76 If the :envvar:`SOURCE_DATE_EPOCH` environment variable is set, 77 *invalidation_mode* will be forced to 78 :attr:`PycInvalidationMode.CHECKED_HASH`. 79 80 .. versionchanged:: 3.7.2 81 The :envvar:`SOURCE_DATE_EPOCH` environment variable no longer 82 overrides the value of the *invalidation_mode* argument, and determines 83 its default value instead. 84 85 86.. class:: PycInvalidationMode 87 88 A enumeration of possible methods the interpreter can use to determine 89 whether a bytecode file is up to date with a source file. The ``.pyc`` file 90 indicates the desired invalidation mode in its header. See 91 :ref:`pyc-invalidation` for more information on how Python invalidates 92 ``.pyc`` files at runtime. 93 94 .. versionadded:: 3.7 95 96 .. attribute:: TIMESTAMP 97 98 The ``.pyc`` file includes the timestamp and size of the source file, 99 which Python will compare against the metadata of the source file at 100 runtime to determine if the ``.pyc`` file needs to be regenerated. 101 102 .. attribute:: CHECKED_HASH 103 104 The ``.pyc`` file includes a hash of the source file content, which Python 105 will compare against the source at runtime to determine if the ``.pyc`` 106 file needs to be regenerated. 107 108 .. attribute:: UNCHECKED_HASH 109 110 Like :attr:`CHECKED_HASH`, the ``.pyc`` file includes a hash of the source 111 file content. However, Python will at runtime assume the ``.pyc`` file is 112 up to date and not validate the ``.pyc`` against the source file at all. 113 114 This option is useful when the ``.pycs`` are kept up to date by some 115 system external to Python like a build system. 116 117 118.. function:: main(args=None) 119 120 Compile several source files. The files named in *args* (or on the command 121 line, if *args* is ``None``) are compiled and the resulting byte-code is 122 cached in the normal manner. This function does not search a directory 123 structure to locate source files; it only compiles files named explicitly. 124 If ``'-'`` is the only parameter in args, the list of files is taken from 125 standard input. 126 127 .. versionchanged:: 3.2 128 Added support for ``'-'``. 129 130When this module is run as a script, the :func:`main` is used to compile all the 131files named on the command line. The exit status is nonzero if one of the files 132could not be compiled. 133 134 135.. seealso:: 136 137 Module :mod:`compileall` 138 Utilities to compile all Python source files in a directory tree. 139