[英]Sorting child elements with lxml based on attribute value
我正在尝试根据属性值对文档中的一些子元素进行排序,而实际排序的函数似乎正在工作,新的排序元素的拼接似乎不是。
from lxml import etree
def getkey(elem):
# Used for sorting elements by @LIN.
# returns a tuple of ints from the exploded @LIN value
# '1.0' -> (1,0)
# '1.0.1' -> (1,0,1)
return tuple([int(x) for x in elem.get('LIN').split('.')])
xml_str = """<Interface>
<Header></Header>
<PurchaseOrder>
<LineItems>
<Line LIN="2.0"></Line>
<Line LIN="3.0"></Line>
<Line LIN="1.0"></Line>
</LineItems>
</PurchaseOrder>
</Interface>"""
root = etree.fromstring(xml_str)
lines = root.findall("PurchaseOrder/LineItems/Line")
lines[:] = sorted(lines, key=getkey)
res_lines = [x.get('LIN') for x in lines]
print res_lines
print etree.tostring(root, pretty_print=True)
当我执行上面的代码时,我会看到lines
列表在打印['1.0', '2.0', '3.0']
时排序正确。 但是,由于tostring()打印出以下内容,因此不会更新XML树。
<Interface>
<Header/>
<PurchaseOrder>
<LineItems>
<Line LIN="2.0"/>
<Line LIN="3.0"/>
<Line LIN="1.0"/>
</LineItems>
</PurchaseOrder>
</Interface>
我从http://effbot.org/zone/element-sort.htm那里得到了关于如何排序的想法,它说拼接应该是我需要更新元素顺序的所有内容,但这似乎不是案子。 我意识到lxml与elementtree不是100%兼容,所以作为一个完整性检查我用elementtree替换了lxml导入并获得了完全相同的结果。
这将排序并写入输出:
import xml.etree.ElementTree as ET
tree = ET.parse("in.xml")
def getkey(elem):
# Used for sorting elements by @LIN.
# returns a tuple of ints from the exploded @LIN value
# '1.0' -> (1,0)
# '1.0.1' -> (1,0,1)
return float(elem.get('LIN'))
container = tree.find("PurchaseOrder/LineItems")
container[:] = sorted(container, key=getkey)
tree.write("new.xml")
或使用您自己的代码进行打印:
import xml.etree.ElementTree as ET
tree = ET.fromstring(xml_str)
def getkey(elem):
# Used for sorting elements by @LIN.
# returns a tuple of ints from the exploded @LIN value
# '1.0' -> (1,0)
# '1.0.1' -> (1,0,1)
return float(elem.get('LIN'))
root = etree.fromstring(xml_str)
lines = root.find("PurchaseOrder/LineItems")
lines[:] = sorted(lines, key=getkey)
输出:
In [12]: print (etree.tostring(root, pretty_print=True))
<Interface>
<Header/>
<PurchaseOrder>
<LineItems>
<Line LIN="1.0"/>
<Line LIN="2.0"/>
<Line LIN="3.0"/>
</LineItems>
</PurchaseOrder>
</Interface>
关键是root.find("PurchaseOrder/LineItems")
,你想要找到LineItems
元素并对其进行排序。
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