使用start事件读取xml不全
要读取一个xml文件中每个
item
节点的
review_id
、
summary
等的子结点,样例如下:
<item>
<review_id>0095693</review_id>
<summary>书本内容</summary>
<polarity>P</polarity>
<text>书本的内容很好,对我很有帮助,就是字体的颜色是紫色的,看就了会觉得不清晰。</text>
<category>book</category>
</item>
完整例子可以从 这里 下载。编程环境为Mac 10.9.2,Python 2.7.6,代码如下:
import sys
import os
from xml.etree.ElementTree import iterparse, tostring
def count_pos_neg(itemfile):
pos_count = 0
neg_count = 0
try:
for event, elem in iterparse(itemfile, events=["start",]):
if elem.tag == "item":
try:
if processItem(elem)['polarity'] == "P":
pos_count += 1
else:
neg_count += 1
except Exception, e:
print >> sys.stderr, "Ignoring item: %s" % e
elem.clear()
except SyntaxError, se:
print >> sys.stderr, se
return pos_count, neg_count
def processItem(item):
""" Process a review.
Implement custom code here. Use 'item.find('tagname').text' to access the properties of a review.
"""
category = item.find("category").text
polarity = item.find("polarity").text
text = item.find("text").text
summary = item.find("summary").text
return {'polarity':polarity,
'summary':summary,
'text':text,
'category':category }
if __name__ == "__main__":
pc, nc = count_pos_neg(itemfile)
问题在于,每碰到第55个
item
节点,就会发生一次
AttruibuteError
,错误信息为
Ignoring item: 'NoneType' object has no attribute 'text'
我在使用
evens=('end',)
进行解析时,没有发生错误。这是否说明之前的错误与使用
start
解析有关?
Caiych
10 years, 9 months ago
Answers
文档 说:
Note
iterparse() only guarantees that it has seen the “>” character of a starting tag when it emits a “start” event, so the attributes are defined, but the contents of the text and tail attributes are undefined at that point. The same applies to the element children; they may or may not be present.
If you need a fully populated element, look for “end” events instead.
start
事件发生时这个元素的子元素还没有解析,所以你应该用
end
事件。
siemen
answered 10 years, 9 months ago