Question

I’m trying to understand what is going on here, specifically how curids is getting set:

 for idx in xrange(0, int(math.ceil(float(len(mids))/chunk))):
            curids = mids[int(idx*chunk):int((idx*chunk)+chunk)]

I’m not sure what the syntax for mids[int(idx*chunk):int((idx*chunk)+chunk)] is trying to do.

Answer 1

It extracts blocks of mids into curids, where each block consists of chunk elements.

If you change the loop to print out the values of int(idx*chunk) and int((idx*chunk)+chunk)], you’ll see that for yourself.

For example, if len(mids)==50 and chunk==12, the indices that would get printed are:

0 12
12 24
24 36
36 48
48 60

These are the starting and ending indices of each slice of mids (the start index is inclusive and the end index is not).

Note that the last value is allowed to go above len(mids), but that’s not a problem given how Python slicing works (it’ll just slice to the end of mids).