How Python uses lxml to read and write XML tutorials

This article mainly for you in detail the Python use lxml read and write XML format files, with a certain reference value, interested in small partners can refer to

It is very convenient to use the lxml package to convert the JSON to an XML file before converting the dataset format.

1. Writing XML files

A) using etree and objectify

From lxml import etree, Objectifye = 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),    e.height (    3  ), E.depth ( 0), etree. ElementTree (Anno_tree). Write ("Text.xml", Pretty_print=true)

The contents of the output Test.xml file are as follows:

"

If you need to add other labels on the basis of Anno_tree, use append:

E2 = objectify. Elementmaker (annotate=false) anno_tree2 = E2.object (  e.name ("person"),  E.bndbox (    e.xmin (+),    E.ymin (E.xmax), E.ymax (+),  e.difficult (0)) Anno_tree.append (ANNO_TREE2)

The above output becomes:

<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>  
b) using etree and 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 ' # must be used with Stringetree. subelement (Size, "height"). Text = ' 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 (+) etree. Subelement (Bndbox, "ymin"). Text = str (etree). Subelement (Bndbox, "Xmax"). Text = str etree. Subelement (Bndbox, "Ymax"). Text = str (+) etree. SUbelement (Key_object, "difficult"). Text = ' 0 ' doc = etree. ElementTree (annotation) doc.write (open ("Test.xml", "W"), Pretty_print=true)
2. Read XML

Here you can use XPath to extract the value of the desired element directly. For example, to get the x, y coordinates of the Test.xml file above:



Tree = Etree.parse ("Test.xml") # get Bboxfor bbox in Tree.xpath ('//bndbox '):  # Gets the contents of the Bndbox element for  corner in bbox.ge Tchildren (): # facilitates Bndbox element under sub-element    print Corner.text  # string type