I have used cElementTree to parse XML files in my application and it works beautifully, however, now I wanted to write some unit tests to check whether the results of my methods return expected results.
In one of my tests I want to check whether a retrieved element from the tree is indeed an Element type:
self.assertIsInstance(myElem, Element, 'Incorrect type for myElem')
When I execute my test, I am getting the following error:
TypeError: isinstance() arg 2 must be a class, type or tuple of classes and types.
What is Element then if it is not a class or a type? I could not find many details about this in the documentation.
I found this excerpt from the source code, File : ElementTree.py
##
# Element factory. This function returns an object implementing the
# standard Element interface. The exact class or type of that object
# is implementation dependent, but it will always be compatible with
# the {@link #_ElementInterface} class in this module.
# <p>
# The element name, attribute names, and attribute values can be
# either 8-bit ASCII strings or Unicode strings.
#
# @param tag The element name.
# @param attrib An optional dictionary, containing element attributes.
# @param **extra Additional attributes, given as keyword arguments.
# @return An element instance.
# @defreturn Element
def Element(tag, attrib={}, **extra):
attrib = attrib.copy()
attrib.update(extra)
return _ElementInterface(tag, attrib)
So, Element is ultimately a factory method.