Question

I have a set of data

data = (1,2,3,4,5,6,7,8,9,10)

Usually in python I’ll group these for display across row of n columns:

cols = 4
grouped = izip_longest(*(iter(data),)*cols)

That gives me a great row display:

grouped = ( (1,2,3,4), (5,6,7,8), (9,10,None,None) )

which , on a templated website, would look like

1  2  3  4
5  6  7  8
9  10

Now i’m trying to wrap my head around a different display – down the column & across n rows

1  4  7  10
2  5  8  
3  6  9

because this is for web templating, I need to generate a set of this data :

grouped = ( (1,4,7,10), (2,5,8,None), (3,6,9,None) )

Honestly, I’m at a complete loss on how to best approach this.

Answer 1

All you need is a call to zip():

In [10]: rows = 3

In [11]: zip(*itertools.izip_longest(*(iter(data),)*rows))
Out[11]: [(1, 4, 7, 10), (2, 5, 8, None), (3, 6, 9, None)]

Basically, it uses exactly the same algorithm as yours, and then transposes the result.