Re: Geneator/Iterator Nesting Problem - Any Ideas? 2.4

[Steven Bethard]

ChaosKCW wrote:
For reasons of pure asthetics and my own learning I wanted it to look
like this:
</B>
def resultsetbatchgen(cursor, size=100):
    for results in (recordbatch for recordbatch in
cursor.fetchmany(size)):
        for rec in results:
            yield rec
</B>
Note that this is equivalent to:
def resultsetbatchgen(cursor, size=100):
    for results in cursor.fetchmany(size):
        for rec in results:
            yield rec
That is, your generator expression isn't really doing anything.
cur.execute(<QUERY WITH MOER THAN 1000 records>)
recs = (recordbatch for recordbatch in cur.fetchmany(1000))
sum(map(lambda x: 1, (rec for rec in recs)))
1000
This should be equivalent to
...
>>> recs = iter(cur.fetchmany(1000))
>>> len(list(recs))
cur.execute(<QUERY WITH MOER THAN 1000 records>)
for results in (recordbatch for recordbatch in cur.fetchmany(1000)):
... 	print sum(map(lambda x: 1, (rec for rec in results)))
This is now equivalent to:
>>> cur.execute(<QUERY WITH MOER THAN 1000 records>)
>>> for rec in cur.fetchmany(1000):
...     print len(list(results))
Note that you're counting the number of elements in record, which I'm 
guessing is 76?

I'm thinking you want to do something like:
def resultsetbatchgen(cursor, size=100):
    while True:
        results = cursor.fetchmany(size)
        if not results:
            break
        for rec in results:
            yield rec
I don't actually know how you tell when there isn't anything more to 
fetch, but if it returns an empty list, you could also write this like:

def resultsetbatchgen(cursor, size=100):
    for results in iter(lambda: cursor.fetchmany(size), [])
        for rec in results:
            yield rec
HTH,
STeVe
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