用python替换xml中的树元素

Question

#!/usr/bin/env python

import libxml2

import os.path

from cfs_utils import *

solvers = ["CG","CGS","BICGSTABL"]
precond = ["saamg","iluk","ssor"]
for s in range(3):
for p in range(3):
   print "s " + str(s)
   problem = "eval_" + str(solvers[s]) + "_" + str(precond[p]) + "_default"

#if os.path.exists(problem + ".info.xml"):
#  continue

print "execute " + problem + "\n"

doc = libxml2.parseFile("simp_lis_solver_3D.xml")
xml = doc.xpathNewContext()
solver = xml.xpathEval('//solverList')
xml.setContextNode(solvers)
solver_name = xml.xpathEval(solvers[s])

Here I want to replace the xml elements with the specified solver Name, I tried in the following way mentoined below but nothing is working out.

  #[0].getContent()
  #  xml.xpathRegisterNs('cfs', 'http://www.cfs++.org')
  #replace(xml, "//cfs:volume/@value", str(vol))
  # replace("pardiso", "CG", "CGS")
for line in doc:
   solvers[s].replace( 'TFQMR', 'CG')
   doc.saveFile(problem + ".xml")
   execute("cfs.rel -m bulk3d_10.mesh " + problem)

Here is the Sample of my Xml file here using this xml file i want to replace the solver TFGMR with the specified solver in my python code.

  <system>
    <solutionStrategy>
      <standard>
        <matrix storage="sparseNonSym"/>
      </standard>
    </solutionStrategy>
    <solverList>
      <lis id="default">
        <precond><saamg/>
        </precond>
        <solver>
        <TFQMR></TFQMR>
    </solver>
        <maxIter>10000</maxIter>
        <tolerance>1.0E-10</tolerance>
        <logging>false</logging>
      </lis>
    </solverList>
  </system>
</linearSystems>

Answer 1

You can remove from the parent and then replace using xml.ElementTree :

from xml.etree import ElementTree as et

tree = et.parse("your.xml")
x  = tree.getroot()


for s in x.findall(".//solver"):
    ch = s.find("./TFQMR")
    if ch is not None:
        s.remove(ch)
        s.append(et.SubElement(s, "CG"))

print(et.tostring(x))

using your snippet:

In [55]: from xml.etree import ElementTree as et

In [56]: tree = et.parse("test.xml")

In [57]: x  = tree.getroot()

In [58]: for s in x.findall(".//solver"):
   ....:     ch = s.find("./TFQMR")
   ....:     if ch is not None:
   ....:             s.remove(ch)
   ....:             s.append(et.SubElement(s, "CG"))
   ....:print(et.tostring(x))
   ....:         
<system>
    <solutionStrategy>
          <standard>
              <matrix storage="sparseNonSym" />
          </standard>
    </solutionStrategy>
    <solverList>
        <lis id="default">
            <precond>
                <saamg />
            </precond>
            <solver>
                <CG /><CG /></solver>
            <maxIter>10000</maxIter>
            <tolerance>1.0E-10</tolerance>
            <logging>false</logging>
         </lis>
    </solverList>
</system>

Using your file, you need to register the namespace:

from xml.etree import ElementTree as et

tree = et.parse(.xml")
x = tree.getroot()

namespaces = {'cfsSimulation': "http://www.cfs++.org"}

solvers = x.findall(
"cfsSimulation:sequenceStep/cfsSimulation:linearSystems/cfsSimulation:system"
"//cfsSimulation:solverList/cfsSimulation:lis/cfsSimulation:solver",namespaces)
for s in solvers:   
    ch = s.find("./cfsSimulation:TFQMR", namespaces)
    if ch is not None:
        s.remove(ch)
        s.append(et.SubElement(s, "CG"))

print(et.tostring(x))