python字典应如何存储在pytables中? [英] How should python dictionaries be stored in pytables?

问题描述

pytables本身不支持python字典.我所采用的方法是制作以下形式的数据结构:

pytables doesn't natively support python dictionaries. The way I've approached it is to make a data structure of the form:

tables_dict = {
'key'         : tables.StringCol(itemsize=40),
'value'       : tables.Int32Col(),
}

(请注意，我确保键的长度小于40个字符)，然后使用以下结构创建表:

(note that I ensure that the keys are <40 characters long) and then create a table using this structure:

file_handle.createTable('/', 'dictionary', tables_dict)

，然后用以下命令填充它:

and then populate it with:

file_handle.dictionary.append(dictionary.items())

并使用以下命令检索数据:

and retrieve data with:

dict(file_handle.dictionary.read())

这可以，但是重新读字典非常慢.我认为问题在于 read()函数导致整个字典被加载到内存中，这实际上不是必须的.有更好的方法吗?

This works ok, but reading the dictionary back in is extremely slow. I think the problem is that the read() function is causing the entire dictionary to be loaded into memory, which shouldn't really be necessary. Is there a better way to do this?

推荐答案

您可以要求PyTables在表内部进行搜索，还可以在键列上创建索引以加快速度.

You can ask PyTables to search inside the table, and also create an index on the key column to speed that up.

要创建索引:

table.cols.key.createIndex()

要查询 key 等于变量 search_key 的值:

[row['value'] for row in table.where('key == search_key')]

http://pytables.github.com/usersguide/optimization.html#searchoptim

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