Home Backend Development Python Tutorial 在Python中marshal对象序列化的相关知识

在Python中marshal对象序列化的相关知识

Jun 10, 2016 pm 03:10 PM
python Serialization

有时候,要把内存中的一个对象持久化保存到磁盘上,或者序列化成二进制流通过网络发送到远程主机上。Python中有很多模块提供了序列化与反序列化的功能,如:marshal, pickle, cPickle等等。今天就讲讲marshal模块。

  •   注意: marshal并不是一个通用的模块,在某些时候它是一个不被推荐使用的模块,因为使用marshal序列化的二进制数据格式还没有文档化,在不同版本的Python中,marshal的实现可能不一样。也就是说,用python2.5序列为一个对象,用python2.6的程序反序列化所得到的对象,可能与原来的对象是不一样的。但这个模块存在的意义,正如Python手册中所说:The marshal module exists mainly to support reading and writing the “pseudo-compiled” code for Python modules of .pyc files.

下面是marshal模块中定义的一些与序列化/反序列化有关的函数:
marshal.dump(value, file[, version])

将值写入到一个打开的输出流里。参数value表示待序列化的值。file表示打开的输出流。如:以”wb”模式打开的文件,sys.stdout或者os.popen。对于一些不支持序列类的类型,dump方法将抛出ValueError异常。要特别说明一下,并不是所有类型的对象都可以使用marshal模块来序列化/反序列化的。在python2.6中,支持的类型包括:None, integers, long integers, floating point numbers, strings, Unicode objects, tuple, list, set, dict, 和 code objects。对于tuple, list, set, dict等集合对象,其中的元素必须也是上述类型之一。
marshal.load(file)

执行与marshal.dump相反的操作,将二进制数据反序列为Python对象。下面是一个例子,演示这两个方法的使用:
 

# coding=gbk
 
import  marshal ,  sys ,  os
 
lst  =  [ 1 ,  ( 2 ,  " string " ) ,  { " key " :  " Value " } ]
 
# 序列化到文件中
fle  =  open ( os . path . join ( os . getcwd ( ) ,  ' fle . txt ' ) ,  ' wb ' )
marshal . dump ( lst ,  fle )
fle . close ( )
 
# 反序列化
fle1  =  open ( os . path . join ( os . getcwd ( ) ,  ' fle . txt ' ) ,  ' rb ' )
lst1  =  marshal . load ( fle1 )
fle1 . close ( )
 
# 打印结果
print  lst
print  lst1
 
# ----  结果  ----
# [1,  (2,  'string'),  {'key':  'Value'}]
# [1,  (2,  'string'),  {'key':  'Value'}]
marshal.dumps(value[, version)
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该方法与上面讲的marshal.dump()功能类似,只是它返回的是序列化之后的二进制流,而不是将这些数据直接写入到文件中。
marsahl.load(string)

将二进制流反序列化为对象。下面的一段代码,演示这两个方法的使用:

import  marshal ,  sys ,  os
 
lst  =  [ 1 ,  ( 2 ,  " string " ) ,  { " key " :  " Value " } ]
 
byt1  =  marshal . dumps ( lst )
lst1  =  marshal . loads ( byt1 )
 
# 打印结果
print  lst
print  lst1
 
# —-  结果  —-
# [1,  (2,  'string'),  {'key':  'Value'}]
# [1,  (2,  'string'),  {'key':  'Value'}]
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更多关于marshal的内容,请参考Python手册。

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