python利用lxml读写xml格式的文件_Python

python利用lxml读写xml格式的文件

2020-12-01 00:32Arkenstone Python

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