Wow, if I'm going to get replies (with implemented solutions!) this quickly, I'll post here more often :-)
That is indeed typical of this most attentive group :-)
Its taken me a while to get a rough understanding of this code, but I
think I have some idea.
It is just an example jotted in 2 min - no doubt it could be made clearer.
No, groupby, groups on the value of record(item), where item is given by iterating over linesourceCorrect me if I'm wrong. groupby groups based on value of line(record)
You should check the itertools documentation: http://docs.python.org/lib/itertools-functions.html
Record returns 1 for the first line, 1 of the second, 1 for the 3rd, then 2 for the 4th because seq[0] gets incremented since len(line) > 20
In this case, it doesn't matter what record returns, as long as it is equal for successive values of item that should be grouped
OK thats fair enough. But how does record retain state between calls? How is that related to the fact your storing your value as a singleton list, instead just an int?
You are asking about the fundamental behavior of Python: argument passing, mutable objects and scopes.
It seems a little confusing to be honest, probably mainly due to my unfamiliarity with groupby. Retaining state between method calls is part of what interests me so much about the Generator/ Acceptor case. Here youre retaining state between calls with none of the special syntax used for example in Generators.
How? Is it a side effect of the way groupby uses record? If so, then thats a littleoblique and unreadable for my liking.
No, it's nothing special about groupby. record simply stores its state in a mutable default parameter. This isn't general good practice: at least you have to be careful with it. You can see the behavior in the following example:
>>> def accumulate(value, accum = []):
... accum.append(value)
... return accum
...
>>> accumulate(1)
[1]
>>> accumulate(2)
[1, 2]
>>> accumulate(6)
[1, 2, 6]
>>>
...
Experimenting is good. So is the the documentation: http://docs.python.org/tut/tut.html
Still, this is fascinating.... going to have to spend some time experimenting with groupby as soon as I get a chance....
Michael
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