如何在构造函数中设置ElementTree Element文本字段

Question

如何从其构造函数中设置ElementTree Element的文本字段？或者,在下面的代码中,为什么root.text的第二次打印无？

import xml.etree.ElementTree as ET

root = ET.fromstring("<period units='months'>6</period>")
ET.dump(root)
print root.text

root=ET.Element('period', {'units': 'months'}, text='6')
ET.dump(root)
print root.text

root=ET.Element('period', {'units': 'months'})
root.text = '6'
ET.dump(root)
print root.text

这里输出:

<period units="months">6</period>
6
<period text="6" units="months" />
None
<period units="months">6</period>
6

Answer 1

构造函数不支持它:

class Element(object):
    tag = None
    attrib = None
    text = None
    tail = None

    def __init__(self, tag, attrib={}, **extra):
        attrib = attrib.copy()
        attrib.update(extra)
        self.tag = tag
        self.attrib = attrib
        self._children = []

如果text作为关键字参数传递给构造函数,则会text向元素添加属性,这是第二个示例中发生的情况.

Answer 2

构造函数不允许它,因为他们认为每次foo=bar添加一个属性是不合适的,除了随机的两个:text和tail

如果你认为这是一个愚蠢的理由去除构造函数的舒适(就像我一样),那么你可以创建自己的元素.我做到了.我把它作为子类并添加了一个parent参数.这允许您仍然使用它与其他一切!

Python 2.7:

import xml.etree.ElementTree as ET

# Note: for python 2.6, inherit from ET._Element
#       python 2.5 and earlier is untested
class TElement(ET.Element):
    def __init__(self, tag, text=None, tail=None, parent=None, attrib={}, **extra):
        super(TextElement, self).__init__(tag, attrib, **extra)

        if text:
            self.text = text
        if tail:
            self.tail = tail
        if not parent == None:   # Issues warning if just 'if parent:'
            parent.append(self)

Python 2.6:

#import xml.etree.ElementTree as ET

class TElement(ET._Element):
    def __init__(self, tag, text=None, tail=None, parent=None, attrib={}, **extra):
        ET._Element.__init__(self, tag, dict(attrib, **extra))

        if text:
            self.text = text
        if tail:
            self.tail = tail
        if not parent == None:
            parent.append(self)