Flagging empty XML results from Findall in ElementTree

Question

I am writing a python script to find various tags in an XML file, and want to have warnings if a particular tag can't be found (indicating our metadata is incomplete). This works fine for an element for which there is only one instance:

try:
    element = tree.find("idinfo/descript/abstract")
    if element is None:
        print "(!) No description/abstract in file"
    print "ABSTRACT: {}".format(element.text)
except:
    print "(!) No description/abstract found"

This loop works for finding all procdate elements, but doesn't give any error message when there are none, either the "if None" or "except" warning versions.

try:
    for element in tree.findall("dataqual/lineage/procstep/procdate"):
        if element is None:
            print "(!) No revision date in file"
        print "REVISION DATE: {}".format(element.text)
except:
    print "(!) No revision date found"

[If I can't actively flag something as empty, that's not a big deal, but it would be nice to be able to alert the user...]

Answer 1

When nothing is found, findall() returns an empty list. Test for that first:

results = tree.findall("dataqual/lineage/procstep/procdate")
if not results:
    print "(!) No revision date found"
else:
    for element in results:
        print "REVISION DATE: {}".format(element.text)

not results suffices, as empty containers test as false in a boolean context.