marshal — 内部 Python 对象序列化 ¶

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此模块包含可以按二进制格式读写 Python 值的函数。格式特定于 Python，但独立于机器架构问题 (如：可以将 Python 值写入 PC 文件，再将文件传输到 Sun，然后在那里读取它)。格式细节有意未文档化；它可能在 Python 版本之间变化 (尽管很少发生)。 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 。 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. 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.

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: booleans, integers, floating point numbers, complex numbers, strings, bytes, bytearrays, tuples, lists, sets, frozensets, dictionaries, and code objects, where it should be understood that tuples, lists, sets, frozensets and dictionaries are only supported as long as the values contained therein are themselves supported. The singletons None , Ellipsis and StopIteration can also be marshalled and unmarshalled. For format version lower than 3, recursive lists, sets and dictionaries cannot be written (see below).

There are functions that read/write files as well as functions operating on bytes-like objects.

模块定义了这些函数：

marshal. dump ( value , file [ , version ] ) ¶

Write the value on the open file. The value must be a supported type. The file must be a writeable 二进制文件 .

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() .

version argument indicates the data format that dump should use (see below).

引发 审计事件 marshal.dumps 采用自变量 value , version .

marshal. load ( file ) ¶

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 . The file must be a readable 二进制文件 .

引发 审计事件 marshal.load 不带自变量。

注意

If an object containing an unsupported type was marshalled with dump() , load() will substitute None for the unmarshallable type.

3.9.7 版改变： 此调用用于引发 code.__new__ audit event for each code object. Now it raises a single marshal.load event for the entire load operation.

marshal. dumps ( value [ , version ] ) ¶

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.

version argument indicates the data format that dumps should use (see below).

引发 审计事件 marshal.dumps 采用自变量 value , version .

marshal. loads ( bytes ) ¶

转换 像字节对象 to a value. If no valid value is found, raise EOFError , ValueError or TypeError . Extra bytes in the input are ignored.

引发 审计事件 marshal.loads 采用自变量 bytes .

3.9.7 版改变： 此调用用于引发 code.__new__ audit event for each code object. Now it raises a single marshal.loads event for the entire load operation.

此外，有定义下列常量：

marshal. version ¶

Indicates the format that the module uses. Version 0 is the historical format, version 1 shares interned strings and version 2 uses a binary format for floating point numbers. Version 3 adds support for object instancing and recursion. The current version is 4.

脚注

1

The name of this module stems from a bit of terminology used by the designers of Modula-3 (amongst others), who use the term “marshalling” for shipping of data around in a self-contained form. Strictly speaking, “to marshal” means to convert some data from internal to external form (in an RPC buffer for instance) and “unmarshalling” for the reverse process.

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