如果您有一个大的 xml 无法放入内存,那么您可以尝试一次序列化它一个元素。例如,假设<root><page/><page/><page/>...</root>
文档结构并忽略可能的命名空间问题:
import xml.etree.cElementTree as etree
def getelements(filename_or_file, tag):
context = iter(etree.iterparse(filename_or_file, events=('start', 'end')))
_, root = next(context) # get root element
for event, elem in context:
if event == 'end' and elem.tag == tag:
yield elem
root.clear() # free memory
with open('output.xml', 'wb') as file:
# start root
file.write(b'<root>')
for page in getelements('sample.xml', 'page'):
if keep(page):
file.write(etree.tostring(page, encoding='utf-8'))
# close root
file.write(b'</root>')
where keep(page)
回报True
if page
应保留,例如:
import re
def keep(page):
# all <revision> elements must have 20xx in them
return all(re.search(r'20\d\d', rev.text)
for rev in page.iterfind('revision'))
为了比较,修改smallxml 文件,您可以:
# parse small xml
tree = etree.parse('sample.xml')
# remove some root/page elements from xml
root = tree.getroot()
for page in root.findall('page'):
if not keep(page):
root.remove(page) # modify inplace
# write to a file modified xml tree
tree.write('output.xml', encoding='utf-8')