Split a python list into other "sublists" i.e smaller lists [duplicate]

I have a python list which runs into 1000's. Something like:

data=["I","am","a","python","programmer".....]

where, len(data)= say 1003

I would now like to create a subset of this list (data) by splitting the orginal list into chunks of 100. So, at the end, Id like to have something like:

data_chunk1=[.....] #first 100 items of list data
data_chunk2=[.....] #second 100 items of list data
.
.
.
data_chunk11=[.....] # remainder of the entries,& its len <=100, len(data_chunk_11)=3

Is there a pythonic way to achieve this task? Obviously I can use data[0:100] and so on, but I am assuming that is terribly non-pythonic and very inefficient.

Many thanks.

Solution 1:

I'd say

chunks = [data[x:x+100] for x in range(0, len(data), 100)]

If you are using python 2.x instead of 3.x, you can be more memory-efficient by using xrange(), changing the above code to:

chunks = [data[x:x+100] for x in xrange(0, len(data), 100)]

Solution 2:

Actually I think using plain slices is the best solution in this case:

for i in range(0, len(data), 100):
    chunk = data[i:i + 100]
    ...

If you want to avoid copying the slices, you could use itertools.islice(), but it doesn't seem to be necessary here.

The itertools() documentation also contains the famous "grouper" pattern:

def grouper(n, iterable, fillvalue=None):
    "grouper(3, 'ABCDEFG', 'x') --> ABC DEF Gxx"
    args = [iter(iterable)] * n
    return izip_longest(fillvalue=fillvalue, *args)

You would need to modify it to treat the last chunk correctly, so I think the straight-forward solution using plain slices is preferable.