"py_compile" --- 编译 Python 源文件
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**源代码:** Lib/py_compile.py

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"py_compile" 模块提供了用来从源文件生成字节码的函数和另一个用于当模块
源文件作为脚本被调用时的函数。

虽然不太常用，但这个函数在安装共享模块时还是很有用的，特别是当一些用户
可能没有权限在包含源代码的目录中写字节码缓存文件时。

exception py_compile.PyCompileError

   当编译文件过程中发生错误时，抛出的异常。

py_compile.compile(file, cfile=None, dfile=None, doraise=False, optimize=-1, invalidation_mode=PycInvalidationMode.TIMESTAMP, quiet=0)

   Compile a source file to byte-code and write out the byte-code
   cache file. The source code is loaded from the file named *file*.
   The byte-code is written to *cfile*, which defaults to the **PEP
   3147**/**PEP 488** path, ending in ".pyc". For example, if *file*
   is "/foo/bar/baz.py" *cfile* will default to
   "/foo/bar/__pycache__/baz.cpython-32.pyc" for Python 3.2.  If
   *dfile* is specified, it is used as the name of the source file in
   error messages instead of *file*.  If *doraise* is true, a
   "PyCompileError" is raised when an error is encountered while
   compiling *file*. If *doraise* is false (the default), an error
   string is written to "sys.stderr", but no exception is raised.
   This function returns the path to byte-compiled file, i.e. whatever
   *cfile* value was used.

   The *doraise* and *quiet* arguments determine how errors are
   handled while compiling file. If *quiet* is 0 or 1, and *doraise*
   is false, the default behaviour is enabled: an error string is
   written to "sys.stderr", and the function returns "None" instead of
   a path. If *doraise* is true, a "PyCompileError" is raised instead.
   However if *quiet* is 2, no message is written, and *doraise* has
   no effect.

   If the path that *cfile* becomes (either explicitly specified or
   computed) is a symlink or non-regular file, "FileExistsError" will
   be raised. This is to act as a warning that import will turn those
   paths into regular files if it is allowed to write byte-compiled
   files to those paths. This is a side-effect of import using file
   renaming to place the final byte-compiled file into place to
   prevent concurrent file writing issues.

   *optimize* controls the optimization level and is passed to the
   built-in "compile()" function.  The default of "-1" selects the
   optimization level of the current interpreter.

   *invalidation_mode* should be a member of the "PycInvalidationMode"
   enum and controls how the generated bytecode cache is invalidated
   at runtime.  The default is "PycInvalidationMode.CHECKED_HASH" if
   the "SOURCE_DATE_EPOCH" environment variable is set, otherwise the
   default is "PycInvalidationMode.TIMESTAMP".

   3.2 版更變: Changed default value of *cfile* to be **PEP
   3147**-compliant.  Previous default was *file* + "'c'" ("'o'" if
   optimization was enabled). Also added the *optimize* parameter.

   3.4 版更變: Changed code to use "importlib" for the byte-code cache
   file writing. This means file creation/writing semantics now match
   what "importlib" does, e.g. permissions, write-and-move semantics,
   etc. Also added the caveat that "FileExistsError" is raised if
   *cfile* is a symlink or non-regular file.

   3.7 版更變: The *invalidation_mode* parameter was added as
   specified in **PEP 552**. If the "SOURCE_DATE_EPOCH" environment
   variable is set, *invalidation_mode* will be forced to
   "PycInvalidationMode.CHECKED_HASH".

   3.7.2 版更變: The "SOURCE_DATE_EPOCH" environment variable no
   longer overrides the value of the *invalidation_mode* argument, and
   determines its default value instead.

   3.8 版更變: The *quiet* parameter was added.

class py_compile.PycInvalidationMode

   A enumeration of possible methods the interpreter can use to
   determine whether a bytecode file is up to date with a source file.
   The ".pyc" file indicates the desired invalidation mode in its
   header. See 已缓存字节码的失效 for more information on how Python
   invalidates ".pyc" files at runtime.

   3.7 版新加入.

   TIMESTAMP

      The ".pyc" file includes the timestamp and size of the source
      file, which Python will compare against the metadata of the
      source file at runtime to determine if the ".pyc" file needs to
      be regenerated.

   CHECKED_HASH

      The ".pyc" file includes a hash of the source file content,
      which Python will compare against the source at runtime to
      determine if the ".pyc" file needs to be regenerated.

   UNCHECKED_HASH

      Like "CHECKED_HASH", the ".pyc" file includes a hash of the
      source file content. However, Python will at runtime assume the
      ".pyc" file is up to date and not validate the ".pyc" against
      the source file at all.

      This option is useful when the ".pycs" are kept up to date by
      some system external to Python like a build system.

py_compile.main(args=None)

   Compile several source files.  The files named in *args* (or on the
   command line, if *args* is "None") are compiled and the resulting
   byte-code is cached in the normal manner.  This function does not
   search a directory structure to locate source files; it only
   compiles files named explicitly. If "'-'" is the only parameter in
   args, the list of files is taken from standard input.

   3.2 版更變: Added support for "'-'".

When this module is run as a script, the "main()" is used to compile
all the files named on the command line.  The exit status is nonzero
if one of the files could not be compiled.

也參考:

  模块 "compileall"
     编译一个目录树中所有 Python 源文件的工具。
