Python:存储/检索/更新大量任意对象
我有数百万条记录要经常存储、检索和删除。这些记录中的每一条都有一个键,但该值不容易翻译成字典,因为它是从我没有编写的模块方法返回的任意Python对象。我知道,像json这样的分层数据结构作为字典工作得更好,而且不确定json在任何情况下是否是首选数据库 我正在考虑将每个条目分别放入一个单独的文件中。有更好的方法吗?使用该模块 您可以将其用作字典,就像在json中一样,但它使用pickle存储对象 从python官方文档:Python:存储/检索/更新大量任意对象,python,pickle,Python,Pickle,我有数百万条记录要经常存储、检索和删除。这些记录中的每一条都有一个键,但该值不容易翻译成字典,因为它是从我没有编写的模块方法返回的任意Python对象。我知道,像json这样的分层数据结构作为字典工作得更好,而且不确定json在任何情况下是否是首选数据库 我正在考虑将每个条目分别放入一个单独的文件中。有更好的方法吗?使用该模块 您可以将其用作字典,就像在json中一样,但它使用pickle存储对象 从python官方文档: import shelve d = shelve.open(filen
import shelve
d = shelve.open(filename) # open -- file may get suffix added by low-level
# library
d[key] = data # store data at key (overwrites old data if
# using an existing key)
data = d[key] # retrieve a COPY of data at key (raise KeyError if no
# such key)
del d[key] # delete data stored at key (raises KeyError
# if no such key)
flag = d.has_key(key) # true if the key exists
klist = d.keys() # a list of all existing keys (slow!)
# as d was opened WITHOUT writeback=True, beware:
d['xx'] = range(4) # this works as expected, but...
d['xx'].append(5) # *this doesn't!* -- d['xx'] is STILL range(4)!
# having opened d without writeback=True, you need to code carefully:
temp = d['xx'] # extracts the copy
temp.append(5) # mutates the copy
d['xx'] = temp # stores the copy right back, to persist it
# or, d=shelve.open(filename,writeback=True) would let you just code
# d['xx'].append(5) and have it work as expected, BUT it would also
# consume more memory and make the d.close() operation slower.
d.close() # close it
使用模块
您可以将其用作字典,就像在json中一样,但它使用pickle存储对象
从python官方文档:
import shelve
d = shelve.open(filename) # open -- file may get suffix added by low-level
# library
d[key] = data # store data at key (overwrites old data if
# using an existing key)
data = d[key] # retrieve a COPY of data at key (raise KeyError if no
# such key)
del d[key] # delete data stored at key (raises KeyError
# if no such key)
flag = d.has_key(key) # true if the key exists
klist = d.keys() # a list of all existing keys (slow!)
# as d was opened WITHOUT writeback=True, beware:
d['xx'] = range(4) # this works as expected, but...
d['xx'].append(5) # *this doesn't!* -- d['xx'] is STILL range(4)!
# having opened d without writeback=True, you need to code carefully:
temp = d['xx'] # extracts the copy
temp.append(5) # mutates the copy
d['xx'] = temp # stores the copy right back, to persist it
# or, d=shelve.open(filename,writeback=True) would let you just code
# d['xx'].append(5) and have it work as expected, BUT it would also
# consume more memory and make the d.close() operation slower.
d.close() # close it
我会评估像berkeleydb、kyoto cabinet或其他数据库这样的关键/价值数据库的使用情况。这将为您提供所有新奇的东西,并更好地处理磁盘空间。在块大小为4096B的文件系统中,一百万个文件占用~4GB,无论对象的大小如何,作为下限,如果对象大于4096B,则大小会增加。我会评估像berkeleydb、kyoto cabinet或其他数据库这样的键/值数据库的使用情况。这将为您提供所有新奇的东西,并更好地处理磁盘空间。在块大小为4096B的文件系统中,一百万个文件占用~4GB—无论对象的大小是什么—作为下限,如果对象大于4096B,则大小会增加。那么它会将所有内容pickle到单个文件中?那么它会将所有内容pickle到单个文件中?