Printing traceback with lxml xml schema validation

Question

I am using lxml package (etree) to take in a xml schema and parse it against xml file using the code.

from lxml import etree
import traceback
schema_file = 'C:/Users/Romi/Desktop/XML Testing/schema.xsd'

def validate(xmlparser, xmlfilename):
try:
    with open(xmlfilename, 'r') as f:
        etree.fromstring(f.read(), xmlparser) 
    return True
except:
    return False

with open(schema_file, 'r') as f:
schema_root = etree.XML(f.read())

schema = etree.XMLSchema(schema_root)
xmlparser = etree.XMLParser(schema=schema)

filenames = ['C:/Users/Romi/Desktop/XML Testing/feed.xml','C:/Users/Romi/Desktop/XML          Testing/feed1.xml' ]
fo = open("C:/Users/Romi/Desktop/XML Testing/result.txt", "r+") 
for filename in filenames:
if validate(xmlparser, filename):
    print "%s validates with the schema." % filename
    #fo.write("%s validates with the schema." % filename)
else:
    print "%s doesn't validate with the schema." % filename
    #fo.write("%s doesn't validate with the schema." % filename)

I am printing error when it doesnt validates but I want to print the entire traceback which points to where it failed exactly give the error and move on to next file for validation.

Any pointers?

Answer 1

You can use the traceback library to print out the stack trace in your exception catching:

http://docs.python.org/2/library/traceback.html#traceback-examples

By the way, it's a good practice to limit your exception handling. I'd change it so it only catches lxml parsing errors - your validate() function will return False if open() fails, for example.

Something along the line of this:

try:
  with open(xmlfilename, 'r') as f:
    return etree.fromstring(f.read(), xmlparser)
except etree.XMLSyntaxError:
  print traceback.format_exc()

Hope that helps!