Python之lxml库学习笔记二

使用XPath查找文本

另一个抽取XML树的文本内容是XPath，
>>> print(html.xpath("string()")) # lxml.etree only!
TEXTTAIL
>>> print(html.xpath("//text()")) # lxml.etree only!
[’TEXT’, ’TAIL’]

如果经常使用，可以包装成一个方法：

>>> build_text_list = etree.XPath("//text()") # lxml.etree only!
>>> print(build_text_list(html))
[’TEXT’, ’TAIL’]

也可以通过getparent方法得到父节点

>>> texts = build_text_list(html)
>>> print(texts[0])
TEXT
>>> parent = texts[0].getparent()
>>> print(parent.tag)
body
>>> print(texts[1])
TAIL
>>> print(texts[1].getparent().tag)
br
You can also find out if it’s normal text content or tail text:
>>> print(texts[0].is_text)
True
>>> print(texts[1].is_text)
False
>>> print(texts[1].is_tail)
True

 

树的迭代：

Elements提供一个树的迭代器可以迭代访问树的元素。

>>> root = etree.Element("root")
>>> etree.SubElement(root, "child").text = "Child 1"
>>> etree.SubElement(root, "child").text = "Child 2"
>>> etree.SubElement(root, "another").text = "Child 3"
>>> print(etree.tostring(root, pretty_print=True))
<root>
<child>Child 1</child>
<child>Child 2</child>
<another>Child 3</another>
</root>

>>> for element in root.iter():
... print("%s - %s" % (element.tag, element.text))
root – None
child - Child 1
child - Child 2
another - Child 3

如果知道感兴趣的tag，可以把tag的名字传给iter方法，起到过滤作用。

>>> for element in root.iter("child"):
... print("%s - %s" % (element.tag, element.text))
child - Child 1
child - Child 2

默认情况下，迭代器得到一个树的所有节点，包括ProcessingInstructions, Comments and Entity的实例。如果想确认只有Elements对象返回，可以把Element factory作为参数传入。

>>> root.append(etree.Entity("#234"))
>>> root.append(etree.Comment("some comment"))
>>> for element in root.iter():
... if isinstance(element.tag, basestring):
... print("%s - %s" % (element.tag, element.text))
... else:
... print("SPECIAL: %s - %s" % (element, element.text))
root - None
child - Child 1
child - Child 2
another - Child 3
SPECIAL: ê - ê
SPECIAL: <!--some comment--> - some comment

>>> for element in root.iter(tag=etree.Element):
... print("%s - %s" % (element.tag, element.text))
root - None
child - Child 1
child - Child 2
another - Child 3
>>> for element in root.iter(tag=etree.Entity):
... print(element.text)
ê