Another way to do this is to use dispatch methods. If you have extra processing to do for each tag, this might be a good way to go.
I'm going to assume that your data lines have the form 'tag=data'. Then your Node class might have methods that look like this:
class Node: ... def parse_metadata(self, line): tag, data = line.split('=', 1) try: handler = getattr(self, 'handle_' + tag) except AttributeError: print 'Unexpected tag:', tag, data else: handler(data)
def handle_something_tag(self, data): self.something = int(data) # for example
def handle_last(self, data): try: self.another_thing.append(data) # attribute is a list except AttributeError: self.another_thing = [data]
and so on. This organization avoids any if / else chain and puts all the processing for each tag in a single place.
One more idea. If you have 20 different tags but only four different ways of processing them, maybe you want to use a dict that maps from the tag name to a tuple of (attribute name, processing method). With this approach you need only four handler methods instead of 20. It would look like this:
metadata_dict = {
'something_tag' : ( 'something', self.handle_int ),
'last' : ( 'another_thing', self.handle_list ),
}def parse_metadata(self, line):
tag, data = line.split('=', 1)
try:
attr_name, handler = metadata_dict[tag]
except AttributeError:
print 'Unexpected tag:', tag, data
else:
handler(attr_name, data)def handle_int(self, attr_name, data): setattr(self, attr_name, int(data))
def handle_list(self, attr_name, data): l = getattr(self, attr_name, []) l.append(data) setattr(self, attr_name, l)
I-have-to-stop-replying-to-my-own-posts-ly yours, Kent
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