Josep M. Fontana wrote:
The only time year is bound is in the previous loop, as I said. It's the
line that goes:
name, year = line.strip.....
So year is whatever it was the last time through that loop.
OK, this makes sense. Indeed that is the value in the last entry for
the dictionary. Thanks a lot again.
Dictionaries don't have a "last", or "first", entry -- they're unordered
collections. Think of them as a bag filled with stuff -- if you reach in
and grab an item, one at a time, you will get the items in some order,
but that's imposed on the bag by the sequential nature of taking one
item at a time. The items themselves have no order.
Iterating over a dictionary, or printing it, is like dipping into the
bag for each item one at a time. Python carefully ensures that this
order is consistent: dict,keys(), dict.values() and dict.items() will
return the objects in the same order, so long as you don't modify the
dictionary between calls. But that order is arbitrary, depends on the
history of insertions and deletions, and is subject to change without
notice. So if we do this:
d = {}
d[0] = 'a'
d[-1] = 'b'
d[-2] = 'c'
and then print d in Python 3.1.1, we get: {0: 'a', -2: 'c', -1: 'b'}
but if we add the items in a different order:
d = {}
d[-2] = 'c'
d[0] = 'a'
d[-1] = 'b'
we get this instead: {0: 'a', -1: 'b', -2: 'c'}.
In general, there is no relationship between the order you insert
objects into a dict and the order that you will get them out. Sometimes
it may match. Usually it won't.
--
Steven
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