the recursive function is parseMML. I want it to parse a MathML expression into a Python one. The simple example mmlinput is por producing the fraction 3/5, but it produces:
['(', '(', '3', ')', '/', '(', '5', ')', '(', '3', ')', '(', '5', ')', ')']
Instead of:
['(', '(', '3', ')', '/', '(', '5', ')', ')']
Because I don't know how to get rid of the elements entered already recursively. Any ideas about how to skip them?
Thanks
mmlinput='''<?xml version="1.0"?> <math xmlns="http://www.w3.org/1998/Math/MathML" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.w3.org/1998/Math/MathML http://www.w3.org/Math/XMLSchema/mathml2/mathml2.xsd"> <mrow> <mfrac> <mrow> <mn>3</mn> </mrow> <mrow> <mn>5</mn> </mrow> </mfrac> </mrow> </math>'''
def parseMML(mmlinput):
from lxml import etree
from StringIO import *
from lxml import objectify
exppy=[]
events = ("start", "end")
context = etree.iterparse(StringIO(mmlinput),events=events)
for action, elem in context:
if (action=='start') and (elem.tag=='mrow'):
exppy+='('
if (action=='end') and (elem.tag=='mrow'):
exppy+=')'
if (action=='start') and (elem.tag=='mfrac'):
mmlaux=etree.tostring(elem[0])
exppy+=parseMML(mmlaux)
exppy+='/'
mmlaux=etree.tostring(elem[1])
exppy+=parseMML(mmlaux)
if action=='start' and elem.tag=='mn': #this is a number
exppy+=elem.text
return (exppy)
The problem is that you're parsing the subtrees within the mfrac
tag twice, because you're parsing it recursively. A quick fix would be to count the recursion level:
mmlinput = "<math> <mrow> <mfrac> <mrow> <mn>3</mn> </mrow> <mrow> <mn>5</mn> </mrow> </mfrac> </mrow> </math>"
def parseMML(mmlinput):
from lxml import etree
from StringIO import *
from lxml import objectify
exppy=[]
events = ("start", "end")
level = 0
context = etree.iterparse(StringIO(mmlinput),events=events)
for action, elem in context:
if (action=='start') and (elem.tag=='mfrac'):
level += 1
mmlaux=etree.tostring(elem[0])
exppy+=parseMML(mmlaux)
exppy+='/'
mmlaux=etree.tostring(elem[1])
exppy+=parseMML(mmlaux)
if (action=='end') and (elem.tag=='mfrac'):
level -= 1
if level:
continue
if (action=='start') and (elem.tag=='mrow'):
exppy+='('
if (action=='end') and (elem.tag=='mrow'):
exppy+=')'
if action=='start' and elem.tag=='mn': #this is a number
exppy+=elem.text
return (exppy)
Note: I had to remove the namespace to make this work, as elem.tag
returns the fully qualified tag name for me. Also you're using +=
to add strings to a list. For single character strings that may work, but +
on a list works like calling extend
, so:
>>> lst = []
>>> lst += 'spam'
>>> lst
['s', 'p', 'a', 'm']
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.