Overview

xcheck is used to validate xml in Python. It requires ElementTree version 1.1.3. Most features can be used with other versions of ElementTree.

XCheck objects can:

• use different rules to determine the content of XML elements

• validate ordered and unordered elements

• validate attributes and contents of elements

• xcheck objects are callable, and can check:

  • real data
  • strings that represent real data
  • ElementTree.Element objects
  • Text representing an ElementTree.Element object

The xchecx module makes a few assumtions about XML-data, which, as I see it, as a few limitations:

• No Meaningful Mixed Content: an element has either text or children, but not both.
• Whitespace between children of an element is ignored. This allows the XML to be written with human-readable line breaks.
• Spaces around an element’s text is ignored. This means <x>a</a> and <x> a </x> are considered the same element and validate the same.

Note

Currently, XCheck objects do not deal with namespaces.

XCheck objects are called directly to check data:

>>> from xcheck import TextCheck
>>> nameCh = TextCheck('name', minLength = 2)
>>> nameCh('Josh')
True
>>> nameCh('J')

Traceback (most recent call last):
  File "<pyshell#3>", line 1, in <module>
    name('J')
  File "C:\Python26\lib\site-packages\xcheck\xcheck.py", line 391, in __call__
    ok = self.checkContent(arg)
  File "C:\Python26\lib\site-packages\xcheck\xcheck.py", line 671, in checkContent
    raise self.error, "Text too short"
XCheckError: Text too short
>>> nameCh('<name>Josh</name>')
True
>>> from elementtree import ElementTree as ET
>>> josh = ET.Element('name')
>>> josh.text = 'Josh'
>>> ET.dump(josh)
<name>Josh</name>
>>> nameCh(josh)
True
>>>

The xcheck module defines the following classes:

Checker	Data to be checked
XCheck	The base checker, used for parent XML nodes
TextCheck	Generic texts
EmailCheck	Email Addresses
URLCheck	URLs
IntCheck	Integers
DecimalCheck	Floats
DatetimeCheck	Dates and times
BoolCheck	Boolean values
SelectionCheck	Choice of various strings
ListCheck	Lists of strings with filtering

Other Helpful Things

There are two extra tools that XMLCheck defines to make working with XML easier.

Wrap

The Wrap provides an interface between a checker and an element, creating a Python object:

>>> from xcheck import XCheck, TextCheck, Wrap
>>> first = TextCheck('first', minLength = 2)
>>> last = TextCheck('last', minLength = 2)
>>> nameCh = XCheck('name', children = [first, last])
>>> from elementtree import ElementTree as ET
>>> name = ET.Element('name')
>>> fname = ET.SubElement(name, 'first')
>>> fname.text = 'Josh'
>>> lname = ET.SubElement(name, 'last')
>>> lname.text = 'English'
>>> ET.dump(name)
'<name><first>Josh</first><last>English</last></name>'
>>> nameCh(name)
True
>>> nameObj = Wrap(nameCh, name)
>>> nameObj._get_elem_value('first')
'Josh'
>>> nameObj._get_elem_value('last')
'English'

The Wrap class can be subclassed to provide more meaninful attributes.

load_checker()

The load_checker function Creates an XCheck object from a definiton node. The rules for creating a definiton node are outlined in Definition Nodes.