# `marshal` --- 内部使用向けの Python オブジェクト直列化

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`, `dict`, `frozendict` (since `version` 6), `set`, `frozenset`, and `slice` (since `version` 5). 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.

バージョン 3.15 で変更: Added format version 6, which allows marshalling `frozendict`.

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
  6 | Python 3.15 | Support for `frozendict` 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。