"marshal" --- 内部使用向けの Python オブジェクト直列化
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This module contains functions that can read and write Python values
in a binary format.  The format is specific to Python, but independent
of machine architecture issues (e.g., you can write a Python value to
a file on a PC, transport the file to a Mac, and read it back there).
Details of the format are undocumented on purpose; it may change
between Python versions (although it rarely does). [1]

This is not a general "persistence" module.  For general persistence
and transfer of Python objects through RPC calls, see the modules
"pickle" and "shelve".  The "marshal" module exists mainly to support
reading and writing the "pseudo-compiled" code for Python modules of
".pyc" files. Therefore, the Python maintainers reserve the right to
modify the marshal format in backward incompatible ways should the
need arise. The format of code objects is not compatible between
Python versions, even if the version of the format is the same. De-
serializing a code object in the incorrect Python version has
undefined behavior. If you're serializing and de-serializing Python
objects, use the "pickle" module instead -- the performance is
comparable, version independence is guaranteed, and pickle supports a
substantially wider range of objects than marshal.

警告:

  The "marshal" module is not intended to be secure against erroneous
  or maliciously constructed data.  Never unmarshal data received from
  an untrusted or unauthenticated source.

bytes-like オブジェクトを操作する関数と同様に、ファイルの読み書きを行
う関数が提供されています。

Not all Python object types are supported; in general, only objects
whose value is independent from a particular invocation of Python can
be written and read by this module.  The following types are
supported:

* Numeric types: "int", "bool", "float", "complex".

* Strings ("str") and "bytes". *Bytes-like objects* like "bytearray"
  are marshalled as "bytes".

* Containers: "tuple", "list", "set", "frozenset", and (since
  "version" 5), "slice". It should be understood that these are
  supported only if the values contained therein are themselves
  supported. Recursive containers are supported since "version" 3.

* The singletons "None", "Ellipsis" and "StopIteration".

* "code" objects, if *allow_code* is true. See note above about
  version dependence.

バージョン 3.4 で変更:

* Added format version 3, which supports marshalling recursive lists,
  sets and dictionaries.

* Added format version 4, which supports efficient representations of
  short strings.

バージョン 3.14 で変更: Added format version 5, which allows
marshalling slices.

このモジュールでは、以下の関数が定義されています。

marshal.dump(value, file, version=version, /, *, allow_code=True)

   開かれたファイルに値を書き込みます。値はサポートされている型でなく
   てはなりません。file は書き込み可能な  *バイナリファイル* である必
   要があります。

   If the value has (or contains an object that has) an unsupported
   type, a "ValueError" exception is raised --- but garbage data will
   also be written to the file.  The object will not be properly read
   back by "load()". Code objects are only supported if *allow_code*
   is true.

   *version* 引数は "dump" が使用するデータフォーマットを指定します (
   下記を参照してください)。

   引数 "value", "version" を指定して 監査イベント "marshal.dumps" を
   送出します。

   バージョン 3.13 で変更: Added the *allow_code* parameter.

marshal.load(file, /, *, allow_code=True)

   Read one value from the open file and return it.  If no valid value
   is read (e.g. because the data has a different Python version's
   incompatible marshal format), raise "EOFError", "ValueError" or
   "TypeError". Code objects are only supported if *allow_code* is
   true. The file must be a readable *binary file*.

   引数無しで 監査イベント "marshal.load" を送出します。

   注釈:

     サポートされていない型を含むオブジェクトが "dump()" で整列化され
     ている場合、 "load()" は整列化不能な値を "None" で置き換えます。

   バージョン 3.10 で変更: This call used to raise a "code.__new__"
   audit event for each code object. Now it raises a single
   "marshal.load" event for the entire load operation.

   バージョン 3.13 で変更: Added the *allow_code* parameter.

marshal.dumps(value, version=version, /, *, allow_code=True)

   Return the bytes object that would be written to a file by
   "dump(value, file)".  The value must be a supported type.  Raise a
   "ValueError" exception if value has (or contains an object that
   has) an unsupported type. Code objects are only supported if
   *allow_code* is true.

   *version* 引数は "dumps" が使用するデータフォーマットを指定します (
   下記を参照してください)。

   引数 "value", "version" を指定して 監査イベント "marshal.dumps" を
   送出します。

   バージョン 3.13 で変更: Added the *allow_code* parameter.

marshal.loads(bytes, /, *, allow_code=True)

   Convert the *bytes-like object* to a value.  If no valid value is
   found, raise "EOFError", "ValueError" or "TypeError". Code objects
   are only supported if *allow_code* is true. Extra bytes in the
   input are ignored.

   引数 "bytes" を指定して 監査イベント "marshal.loads" を送出します。

   バージョン 3.10 で変更: This call used to raise a "code.__new__"
   audit event for each code object. Now it raises a single
   "marshal.loads" event for the entire load operation.

   バージョン 3.13 で変更: Added the *allow_code* parameter.

これに加えて、以下の定数が定義されています:

marshal.version

   Indicates the format that the module uses. Version 0 is the
   historical first version; subsequent versions add new features.
   Generally, a new version becomes the default when it is introduced.

   +---------+-----------------+------------------------------------------------------+
   | Version | Available since | 新しい機能                                           |
   |=========|=================|======================================================|
   | 1       | Python 2.4      | Sharing interned strings                             |
   +---------+-----------------+------------------------------------------------------+
   | 2       | Python 2.5      | Binary representation of floats                      |
   +---------+-----------------+------------------------------------------------------+
   | 3       | Python 3.4      | Support for object instancing and recursion          |
   +---------+-----------------+------------------------------------------------------+
   | 4       | Python 3.4      | Efficient representation of short strings            |
   +---------+-----------------+------------------------------------------------------+
   | 5       | Python 3.14     | Support for "slice" objects                          |
   +---------+-----------------+------------------------------------------------------+

-[ 脚注 ]-

[1] このモジュールの名前は (特に) Modula-3 の設計者の間で使われていた
    用語の一つに由来しています。彼らはデータを自己充足的な形式で輸送す
    る操作に "整列化 (marshalling)" という用語を使いました。厳密に言え
    ば、"整列させる (to marshal)" とは、あるデータを (例えば RPC バッ
    ファのように) 内部表現形式から外部表現形式に変換することを意味し、
    "非整列化 (unmarshalling)" とはその逆を意味します。
