编写Python工具以将XML转换为Python? [英] Writing a Python tool to convert XML to Python?
问题描述
我被要求研究是否可以将 XML 转换为Python，以便将XML可以逐步淘汰当前流程它们将被新的python脚本取代.
I've been asked to look in to the possibility of converting XML to Python, so that the XML can be phased out of the current process & they'd be replaced with new python scripts.
当前，XML文件由python&ASP，基本上看起来像这样；
Currently the XML files are used by python & ASP and look essentially like this;
<?xml version="1.0" encoding="UTF-8"?>
<script>
<stage id="stage1" nextStage="stage2">
<initialise>
<variable id="year" value="2012" type="Integer"/>
<executeMethod class="engineclass_date" method="getTodayAsString">
<arguments>
<variable id="someVar"/>
</arguments>
<return>
<variable id="todaysDate"/>
</return>
</executeMethod>
感谢 Pepr 我没有解析器/编译器.处理所有可能的元素仍然需要大量的工作，但是它确实有效，希望其他人可以像我一样从中学到东西！
Thanks to Pepr I've not got a parser/compiler in the works that produces Python code from the XML. It still needs a lot of work to handle all the possible elements, but it works, and hopefully others can learn from this like I am!
仍然需要找到一种方法来为脚本的每个阶段编写一个单独的文件，以使缩进功能正常运行并正确处理错误.
Still need to find a way to write a separate file for each stage of the script in order for the indent to function properly and handle errors properly.
推荐答案
使用标准的 xml.etree.Element 树以将信息从XML提取到Python对象(或增强型第三方 lxml 使用相同的API).
Use the standard xml.etree.Element tree to extract the information from XML to Python objects (or the more enhanced third party lxml with the same API).
我建议阅读Mark Pilrim的 Dive Into Python 3 ，第12章.XML(
I recommend to read the Mark Pilrim's Dive Into Python 3, Chapter 12. XML (http://getpython3.com/diveintopython3/xml.html).
这是解析器/编译器如何编写的核心.想法是递归地遍历元素，收集必要的信息，并在可能的情况下输出代码:
Here is the core of how the parser/compiler could be written. The idea is to go recursively through the elements, collect the neccessary information and output the code when it is possible:
import xml.etree.ElementTree as ET
class Parser:
def __init__(self):
self.output_list = [] # collected output lines
self.il = 0 # indentation level
def __iter__(self):
return iter(self.output_list)
def out(self, s):
'''Output the indented string to the output list.'''
self.output_list.append(' ' * self.il + s)
def indent(self, num=1):
'''Increase the indentation level.'''
self.il += num
def dedent(self, num=1):
'''Decrease the indentation level.'''
self.il -= num
def parse(self, elem):
'''Call the parser of the elem.tag name.
The tag name appended to "parse_" and then the name of that
function is called. If the function is not defined, then
self.parse_undefined() is called.'''
fn_name = 'parse_' + elem.tag
try:
fn = getattr(self, fn_name)
except AttributeError:
fn = self.parse_undefined
return fn(elem)
def loop(self, elem):
'''Helper method to loop through the child elements.'''
for e in elem:
self.parse(e)
def parseXMLfile(self, fname):
'''Reads the XML file and starts parsing from the root element.'''
tree = ET.parse(fname)
script = tree.getroot()
assert script.tag == 'script'
self.parse(script)
###################### ELEMENT PARSERS #######################
def parse_undefined(self, elem):
'''Called for the element that has no parser defined.'''
self.out('PARSING UNDEFINED for ' + elem.tag)
def parse_script(self, elem):
self.loop(elem)
def parse_stage(self, elem):
self.out('')
self.out('Parsing the stage: ' + elem.attrib['id'])
self.indent()
self.loop(elem)
self.dedent()
def parse_initialise(self, elem):
self.out('')
self.out('#---------- ' + elem.tag + ' ----------')
self.loop(elem)
def parse_variable(self, elem):
tt = str # default type
if elem.attrib['type'] == 'Integer':
tt = int
# elif ... etc for other types
# Conversion of the value to the type because of the later repr().
value = tt(elem.attrib['value'])
id_ = elem.attrib['id']
# Produce the line of the output.
self.out('{0} = {1}'.format(id_, repr(value)))
def parse_execute(self, elem):
self.out('')
self.out('#---------- ' + elem.tag + ' ----------')
self.loop(elem)
def parse_if(self, elem):
assert elem[0].tag == 'condition'
condition = self.parse(elem[0])
self.out('if ' + condition + ':')
self.indent()
self.loop(elem[1:])
self.dedent()
def parse_condition(self, elem):
assert len(elem) == 0
return elem.text
def parse_then(self, elem):
self.loop(elem)
def parse_else(self, elem):
self.dedent()
self.out('else:')
self.indent()
self.loop(elem)
def parse_error(self, elem):
assert len(elem) == 0
errorID = elem.attrib.get('errorID', None)
fieldID = elem.attrib.get('fieldID', None)
self.out('error({0}, {1})'.format(errorID, fieldID))
def parse_setNextStage(self, elem):
assert len(elem) == 0
self.out('setNextStage --> ' + elem.text)
if __name__ == '__main__':
parser = Parser()
parser.parseXMLfile('data.xml')
for s in parser:
print s
与此处粘贴的数据 http://pastebin.com/vRRxfWiA 一起使用时，脚本将产生以下内容输出:
When used with the data pasted here http://pastebin.com/vRRxfWiA, the script produces the following output:
Parsing the stage: stage1
#---------- initialise ----------
taxyear = 2012
taxyearstart = '06/04/2012'
taxyearend = '05/04/2013'
previousemergencytaxcode = '747L'
emergencytaxcode = '810L'
nextemergencytaxcode = '810L'
...
maxLimitAmount = 0
PARSING UNDEFINED for executeMethod
if $maxLimitReached$ == True:
employeepayrecord = 'N'
employeepayrecordstate = '2'
else:
employeepayrecordstate = '1'
gender = ''
genderstate = '1'
title = ''
forename = ''
forename2 = ''
surname = ''
dob = ''
dobinvalid = ''
#---------- execute ----------
if $dobstring$ != "":
validDOBCheck = 'False'
PARSING UNDEFINED for executeMethod
if $validDOBCheck$ == False:
error(224, dob)
else:
minimumDOBDate = ''
PARSING UNDEFINED for executeMethod
validDOBCheck = 'False'
PARSING UNDEFINED for executeMethod
if $validDOBCheck$ == False:
error(3007161, dob)
if $dobstring$ == "01/01/1901":
error(231, dob)
else:
error(231, dob)
Parsing the stage: stage2
#---------- initialise ----------
address1 = ''
...
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