"runpy" --- Locating and executing Python modules
*************************************************

**ソースコード:** Lib/runpy.py

======================================================================

"runpy" モジュールは Python のモジュールをインポートせずにその位置を特
定したり実行したりするのに使われます。その主な目的はファイルシステムで
はなく Python のモジュール名前空間を使って位置を特定したスクリプトの実
行を可能にする "-m" コマンドラインスイッチを実装することです。

これはサンドボックスモジュール *ではない* ことに注意してください。すべ
てのコードは現在のプロセスで実行され、あらゆる副作用 (たとえば他のモジ
ュールのキャッシュされたインポート等) は関数から戻った後にそのまま残り
ます。

さらに、 "runpy" 関数から戻った後で、実行されたコードによって定義され
た任意の関数およびクラスが正常に動作することは保証されません。この制限
が受け入れられないユースケースでは、 "importlib" がこのモジュールより
適切な選択となるでしょう。

"runpy" モジュールは2つの関数を提供しています:

runpy.run_module(mod_name, init_globals=None, run_name=None, alter_sys=False)

   Execute the code of the specified module and return the resulting
   module globals dictionary. The module's code is first located using
   the standard import mechanism (refer to **PEP 302** for details)
   and then executed in a fresh module namespace.

   The *mod_name* argument should be an absolute module name. If the
   module name refers to a package rather than a normal module, then
   that package is imported and the "__main__" submodule within that
   package is then executed and the resulting module globals
   dictionary returned.

   The optional dictionary argument *init_globals* may be used to pre-
   populate the module's globals dictionary before the code is
   executed. The supplied dictionary will not be modified. If any of
   the special global variables below are defined in the supplied
   dictionary, those definitions are overridden by "run_module()".

   The special global variables "__name__", "__spec__", "__file__",
   "__cached__", "__loader__" and "__package__" are set in the globals
   dictionary before the module code is executed (Note that this is a
   minimal set of variables - other variables may be set implicitly as
   an interpreter implementation detail).

   "__name__" は、オプション引数 *run_name* が "None" でない場合、指定
   されたモジュールがパッケージであれば "mod_name + '.__main__'" に、
   そうでなければ *mod_name* 引数の値がセットされます。

   "__spec__" will be set appropriately for the *actually* imported
   module (that is, "__spec__.name" will always be *mod_name* or
   "mod_name + '.__main__", never *run_name*).

   "__file__", "__cached__", "__loader__" and "__package__" are set as
   normal based on the module spec.

   引数 *alter_sys* が与えられて "True" に評価されるならば、
   "sys.argv[0]" は "__file__" の値で更新され "sys.modules[__name__]"
   は実行されるモジュールの一時的モジュールオブジェクトで更新されます
   。 "sys.argv[0]" と "sys.modules[__name__]" はどちらも関数が処理を
   戻す前にもとの値に復旧します。

   Note that this manipulation of "sys" is not thread-safe. Other
   threads may see the partially initialised module, as well as the
   altered list of arguments. It is recommended that the "sys" module
   be left alone when invoking this function from threaded code.

   参考: コマンドラインから、 "-m" オプションを与えることで同じ機能を実現
       出来ます。

   バージョン 3.1 で変更: Added ability to execute packages by looking
   for a "__main__" submodule.

   バージョン 3.2 で変更: "__cached__" グローバル変数が追加されました
   (**PEP 3147** を参照)。

   バージョン 3.4 で変更: Updated to take advantage of the module spec
   feature added by **PEP 451**. This allows "__cached__" to be set
   correctly for modules run this way, as well as ensuring the real
   module name is always accessible as "__spec__.name".

runpy.run_path(path_name, init_globals=None, run_name=None)

   Execute the code at the named filesystem location and return the
   resulting module globals dictionary. As with a script name supplied
   to the CPython command line, the supplied path may refer to a
   Python source file, a compiled bytecode file or a valid "sys.path"
   entry containing a "__main__" module (e.g. a zipfile containing a
   top-level "__main__.py" file).

   For a simple script, the specified code is simply executed in a
   fresh module namespace. For a valid "sys.path" entry (typically a
   zipfile or directory), the entry is first added to the beginning of
   "sys.path". The function then looks for and executes a "__main__"
   module using the updated path. Note that there is no special
   protection against invoking an existing "__main__" entry located
   elsewhere on "sys.path" if there is no such module at the specified
   location.

   The optional dictionary argument *init_globals* may be used to pre-
   populate the module's globals dictionary before the code is
   executed. The supplied dictionary will not be modified. If any of
   the special global variables below are defined in the supplied
   dictionary, those definitions are overridden by "run_path()".

   The special global variables "__name__", "__spec__", "__file__",
   "__cached__", "__loader__" and "__package__" are set in the globals
   dictionary before the module code is executed (Note that this is a
   minimal set of variables - other variables may be set implicitly as
   an interpreter implementation detail).

   "__name__" は、オプション引数 *run_name* が "None" でない場合、
   *run_name* に設定され、それ以外の場合は "'<run_path>'" に設定されま
   す。

   If the supplied path directly references a script file (whether as
   source or as precompiled byte code), then "__file__" will be set to
   the supplied path, and "__spec__", "__cached__", "__loader__" and
   "__package__" will all be set to "None".

   If the supplied path is a reference to a valid "sys.path" entry,
   then "__spec__" will be set appropriately for the imported
   "__main__" module (that is, "__spec__.name" will always be
   "__main__"). "__file__", "__cached__", "__loader__" and
   "__package__" will be set as normal based on the module spec.

   A number of alterations are also made to the "sys" module. Firstly,
   "sys.path" may be altered as described above. "sys.argv[0]" is
   updated with the value of "path_name" and "sys.modules[__name__]"
   is updated with a temporary module object for the module being
   executed. All modifications to items in "sys" are reverted before
   the function returns.

   Note that, unlike "run_module()", the alterations made to "sys" are
   not optional in this function as these adjustments are essential to
   allowing the execution of "sys.path" entries. As the thread-safety
   limitations still apply, use of this function in threaded code
   should be either serialised with the import lock or delegated to a
   separate process.

   参考: コマンドラインから インターフェイスオプション で同じ機能を使えま
       す ("python path/to/script")。

   バージョン 3.2 で追加.

   バージョン 3.4 で変更: Updated to take advantage of the module spec
   feature added by **PEP 451**. This allows "__cached__" to be set
   correctly in the case where "__main__" is imported from a valid
   "sys.path" entry rather than being executed directly.

参考:

  **PEP 338** - モジュールをスクリプトとして実行する
     PEP written and implemented by Nick Coghlan.

  **PEP 366** - main モジュールの明示的な相対インポート
     PEP written and implemented by Nick Coghlan.

  **PEP 451** -- インポートシステムのための ModuleSpec 型
     PEP written and implemented by Eric Snow

  コマンドラインと環境 - CPython コマンドライン詳細

  "importlib.import_module()" 関数
