On 17/05/2011 19:02, Joe Leonardo wrote:
Hey all,
Totally baffled by this…maybe I need a nap. Writing a small function to
reject input that is not a list of 19 fields.
def breakLine(value):
if value.__class__() != [] and value.__len__() != 19:
print 'You must pass a list that contains 19 fields.'
else:
print 'YAY!'
If I pass:
breakLine([])
I get:
YAY!
I expect:
You must pass a list that contains 19 fields.
If I print len(value) I get: 0
What is going on here?
If value is [], then value.__class__() is [], so value.__class__() !=
[] is False.
What you meant was:
if value.__class__() != [] or value.__len__() != 19:
print 'You must pass a list that contains 19 fields.'
else:
print 'YAY!'
although the Pythonic way to write it would be:
if not isinstance(value, list) or len(value) != 19:
print 'You must pass a list that contains 19 fields.'
else:
print 'YAY!'
or, even better:
if isinstance(value, list) and len(value) == 19:
print 'YAY!'
else:
print 'You must pass a list that contains 19 fields.'
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