如何使用lxml解析这个巨大的XML文件与嵌套元素的有效方法？

我尝试使用 XML minidom解析这个巨大的XML文档.虽然它在示例文件上运行良好,但在尝试处理真实文件时(约400 MB)它会阻塞系统.

我尝试从codereview为我的xml文件调整代码(它以流式方式处理数据而不是一次性内存加载),由于元素的嵌套特性,我无法隔离数据集.我之前处理过简单的XML文件,但不是像这样的内存密集型任务.

这是正确的方法吗？
如何将清单和发布者ID与每本书相关联？这就是我计划最终将两个表联系起来的方式.

任何反馈都非常感谢.

是book.xml

<BookDatabase>
    <BookHeader>
        <Name>BookData</Name>
        <BookUniverse>All</BookUniverse>
        <AsOfDate>2010-05-02</AsOfDate>
        <Version>1.1</Version>
    </BookHeader>

    <InventoryBody>
        <Inventory ID="12">
            <PublisherClass ID="34">
                <Publisher>
                    <PublisherDetails>
                        <Name>Microsoft Press</Name>
                        <Type>Tech</Type>
                        <ID>7462</ID>
                    </PublisherDetails>
                </Publisher>
            </PublisherClass>
            <BookList>
                <Listing>
                    <BookListSummary>
                        <Date>2009-01-30</Date>
                    </BookListSummary>
                    <Book>
                        <BookDetail ID="67">
                            <BookName>Code Complete 2</BookName>
                            <Author>Steve McConnell</Author>
                            <Pages>960</Pages>
                            <ISBN>0735619670</ISBN>
                        </BookDetail>
                        <BookDetail ID="78">
                            <BookName>Application Architecture Guide 2</BookName>
                            <Author>Microsoft Team</Author>
                            <Pages>496</Pages>
                            <ISBN>073562710X</ISBN>
                        </BookDetail>
                    </Book>
                </Listing>
            </BookList>
        </Inventory>
        <Inventory ID="64">
            <PublisherClass ID="154">
                <Publisher>
                    <PublisherDetails>
                        <Name>O'Reilly Media</Name>
                        <Type>Tech</Type>
                        <ID>7484</ID>
                    </PublisherDetails>
                </Publisher>
            </PublisherClass>
            <BookList>
                <Listing>
                    <BookListSummary>
                        <Date>2009-03-30</Date>
                    </BookListSummary>
                    <Book>
                        <BookDetail ID="98">
                            <BookName>Head First Design Patterns</BookName>
                            <Author>Kathy Sierra</Author>
                            <Pages>688</Pages>
                            <ISBN>0596007124</ISBN>
                        </BookDetail>
                    </Book>
                </Listing>
            </BookList>
        </Inventory>
    </InventoryBody>
</BookDatabase>

Python代码：

import sys
import os
#import MysqLdb
from lxml import etree

CATEGORIES = set(['BookHeader','Inventory','PublisherClass','PublisherDetails','BookDetail'])
SKIP_CATEGORIES = set(['BookHeader'])
DATA_ITEMS = ["Name","Type","ID","BookName","Author","Pages","ISBN"]

def clear_element(element):
    element.clear()
    while element.getprevIoUs() is not None:
        del element.getparent()[0]

def extract_book_elements(context):
    for event,element in context:
         if element.tag in CATEGORIES:
               yield element
               clear_element(element)                 

def fast_iter2(context):
    for bookCounter,element in enumerate(extract_book_elements(context)):
            books = [book.text for book in element.findall("BookDetail")]
            bookdetail = {
                'element' : element.tag,'ID' : element.get('ID')
            }
            for data_item in DATA_ITEMS:
                data = element.find(data_item)
                if data is not None:
                    bookdetail[data_item] = data

            if bookdetail['element'] not in SKIP_CATEGORIES:
                #populate_database(bookdetail,books,cursor)
                print bookdetail,books

            print "========>",bookCounter,"<======="

def main():
        #cursor = connectToDatabase()
        #cursor.execute("""SET NAMES utf8""")

        context = etree.iterparse("book.xml",events=("start","end"))
        #fast_iter(context,cursor)
        fast_iter2(context)

        #cursor.close()


if __name__ == '__main__':
    main()

Python输出：

$python lxmletree_book.py 
========> 0 <=======
========> 1 <=======
{'ID': '12','element': 'Inventory'} []
========> 2 <=======
{'ID': '34','element': 'PublisherClass'} []
========> 3 <=======
{'Name': <Element Name at 0x105140af0>,'Type': <Element Type at 0x105140b40>,'ID': <Element ID at 0x105140b90>,'element': 'PublisherDetails'} []
========> 4 <=======
{'ID': None,'element': 'PublisherDetails'} []
========> 5 <=======
{'ID': None,'element': 'PublisherClass'} []
========> 6 <=======
{'ISBN': <Element ISBN at 0x105140eb0>,'Name': <Element Name at 0x105140dc0>,'Author': <Element Author at 0x105140e10>,'ID': '67','element': 'BookDetail','Pages': <Element Pages at 0x105140e60>} []
========> 7 <=======
{'ID': None,'element': 'BookDetail'} []
========> 8 <=======
{'ISBN': <Element ISBN at 0x1051460a0>,'Name': <Element Name at 0x105140f50>,'Author': <Element Author at 0x105140fa0>,'ID': '78','Pages': <Element Pages at 0x105146050>} []
========> 9 <=======
{'ID': None,'element': 'BookDetail'} []
========> 10 <=======
{'ID': None,'element': 'Inventory'} []
========> 11 <=======
{'ID': '64','element': 'Inventory'} []
========> 12 <=======
{'ID': '154','element': 'PublisherClass'} []
========> 13 <=======
{'Name': <Element Name at 0x105146230>,'Type': <Element Type at 0x105146280>,'ID': <Element ID at 0x1051462d0>,'element': 'PublisherDetails'} []
========> 14 <=======
{'ID': None,'element': 'PublisherDetails'} []
========> 15 <=======
{'ID': None,'element': 'PublisherClass'} []
========> 16 <=======
{'ISBN': <Element ISBN at 0x1051465f0>,'Name': <Element Name at 0x105146500>,'Author': <Element Author at 0x105146550>,'ID': '98','Pages': <Element Pages at 0x1051465a0>} []
========> 17 <=======
{'ID': None,'element': 'BookDetail'} []
========> 18 <=======
{'ID': None,'element': 'Inventory'} []
========> 19 <=======

期望的输出(最终存储在MysqL中 – 现在是Python中的List)：

Publishers
InventoryID PublisherClassID Name            Type ID
12          34               Microsoft Press Tech 7462
64          154              O'Reilly Media  Tech 7484

Books
PublisherID BookDetailID Name                              Author           Pages ISBN
7462        67           Code Complete 2                   Steve McConnell  960   0735619670
7462        78           Application Architecture Guide 2  Microsoft Team   496   073562710X
7484        98           Head First Design Patterns        Kathy Sierra     688   0596007124

您可以尝试这样的事情：

import MysqLdb
from lxml import etree
import config

def fast_iter(context,func,args=[],kwargs={}):
    # http://www.ibm.com/developerworks/xml/library/x-hiperfparse/
    # Author: Liza Daly    
    for event,elem in context:
        func(elem,*args,**kwargs)
        elem.clear()
        while elem.getprevIoUs() is not None:
            del elem.getparent()[0]
    del context

def extract_paper_elements(element,cursor):
    pub={}        
    pub['InventoryID']=element.attrib['ID']
    try:
        pub['PublisherClassID']=element.xpath('PublisherClass/@ID')[0]
    except IndexError:
        pub['PublisherClassID']=None
    pub['PublisherClassID']=element.xpath('PublisherClass/@ID')[0]
    for key in ('Name','Type','ID'):
        try:
            pub[key]=element.xpath(
                'PublisherClass/Publisher/PublisherDetails/{k}/text()'.format(k=key))[0]
        except IndexError:
            pub[key]=None
    sql='''INSERT INTO Publishers (InventoryID,PublisherClassID,Name,Type,ID)
           VALUES (%s,%s,%s)
        '''
    args=[pub.get(key) for key in
          ('InventoryID','PublisherClassID','Name','ID')]
    print(args)
    # cursor.execute(sql,args)
    for bookdetail in element.xpath('descendant::BookList/Listing/Book/BookDetail'):
        pub['BookDetailID']=bookdetail.attrib['ID']
        for key in ('BookName','Author','Pages','ISBN'):
            try:
                pub[key]=bookdetail.xpath('{k}/text()'.format(k=key))[0]
            except IndexError:
                pub[key]=None
        sql='''INSERT INTO Books
               (PublisherID,BookDetailID,Author,Pages,ISBN)
               VALUES (%s,%s)
            '''           
        args=[pub.get(key) for key in
              ('ID','BookDetailID','BookName','ISBN')]
        # cursor.execute(sql,args)
        print(args)


def main():
    context = etree.iterparse("book.xml",events=("end",),tag='Inventory')
    connection=MysqLdb.connect(
        host=config.HOST,user=config.USER,passwd=config.PASS,db=config.MYDB)
    cursor=connection.cursor()

    fast_iter(context,extract_paper_elements,args=(cursor,))

    cursor.close()
    connection.commit()
    connection.close()

if __name__ == '__main__':
    main()

>不要使用fast_iter2. original fast_iter分开了来自特定处理功能的有用实用程序(extract_paper_elements). fast_iter2将两者混合在一起让你没有可重复的代码.>如果在etree.iterparse(“book.xml”中设置tag参数,events =(“end”,tag =’Inventory’)然后是你的处理函数extract_paper_elements只会看到Inventory元素.>给定Inventory元素,您可以使用xpath方法进行挖掘向下并刮掉所需的数据.> args和kwargs参数被添加到fast_iter so cursor中可以传递给extract_paper_elements.