这篇文章主要为大家详细介绍了python利用lxml读写xml格式的文件，具有一定的参考价值，感兴趣的小伙伴们可以参考一下
之前在转换数据集格式的时候需要将json转换到xml文件，用lxml包进行操作非常方便。
1. 写xml文件
a) 用etree和objectify
from lxml import etree, objectify
e = objectify.elementmaker(annotate=false)
anno_tree = e.annotation(
e.folder('voc2014_instance'),
e.filename("test.jpg"),
e.source(
e.database('coco'),
e.annotation('coco'),
e.image('coco'),
e.url("http://test.jpg")
),
e.size(
e.width(800),
e.height(600),
e.depth(3)
),
e.segmented(0),
)
etree.elementtree(anno_tree).write("text.xml", pretty_print=true)
输出的test.xml文件内容如下：
"
如果需要在anno_tree的基础上加其他标签的话用append即可:
e2 = objectify.elementmaker(annotate=false)
anno_tree2 = e2.object(
e.name("person"),
e.bndbox(
e.xmin(100),
e.ymin(200),
e.xmax(300),
e.ymax(400)
),
e.difficult(0)
)
anno_tree.append(anno_tree2)
上面的输出就变成了:
<annotation>
<folder>voc2014_instance/person</folder>
<filename>test.jpg</filename>
<source>
<database>coco</database>
<annotation>coco</annotation>
<image>coco</image>
<url>http://test.jpg</url>
</source>
<size>
<width>800</width>
<height>600</height>
<depth>3</depth>
</size>
<segmented>0</segmented>
<object>
<name>person</name>
<bndbox>
<xmin>100</xmin>
<ymin>200</ymin>
<xmax>300</xmax>
<ymax>400</ymax>
</bndbox>
<difficult>0</difficult>
</object>
</annotation>
b) 用etree和subelement
annotation = etree.element("annotation")
etree.subelement(annotation, "folder").text = "voc2014_instance"
etree.subelement(annotation, "filename").text = "test.jpg"
source = etree.subelement(annotation, "source")
etree.subelement(source, "database").text = "coco"
etree.subelement(source, "annotation").text = "coco"
etree.subelement(source, "image").text = "coco"
etree.subelement(source, "url").text = "http://test.jpg"
size = etree.subelement(annotation, "size")
etree.subelement(size, "width").text ='800' # 必须用string
etree.subelement(size, "height").text = '600'
etree.subelement(size, "depth").text = '3'
etree.subelement(annotation, "segmented").text = '0'
key_object = etree.subelement(annotation, "object")
etree.subelement(key_object, "name").text = “person”
bndbox = etree.subelement(key_object, "bndbox")
etree.subelement(bndbox, "xmin").text = str(100)
etree.subelement(bndbox, "ymin").text = str(200)
etree.subelement(bndbox, "xmax").text = str(300)
etree.subelement(bndbox, "ymax").text = str(400)
etree.subelement(key_object, "difficult").text = '0'
doc = etree.elementtree(annotation)
doc.write(open("test.xml", "w"), pretty_print=true)
2. 读xml
这里可以用xpath直接提取所需的元素的值。比如想要获取上面test.xml文件的x, y坐标：
tree = etree.parse("test.xml")
# get bbox
for bbox in tree.xpath('//bndbox'): # 获取bndbox元素的内容
for corner in bbox.getchildren(): # 便利bndbox元素下的子元素
print corner.text # string类型
以上就是python如何利用lxml对xml进行读写操作教程的详细内容。