r"""
>>> L = [1,2,3,4,5,6,7]


Imperative
==========

>>> def f(L, c):
...     matrix = []
...     row = []
...     for v in L:
...         row.append(v)
...         if len(row) == c:
...             matrix.append(row)
...             row = []
...     if row:
...         for i in range(c - len(row)):
...             row.append(None)
...         matrix.append(row)
...     return matrix
...
>>> def f(L, c):
...     matrix = []
...     for i in range(0, len(L), c):
...         row = L[i:i+c]
...         if len(row) < c:
...             row.extend([None] * (c - len(row)))
...         matrix.append(row)
...     return matrix
...
>>> f(L, 2)
[[1, 2], [3, 4], [5, 6], [7, None]]
>>> f(L, 3)
[[1, 2, 3], [4, 5, 6], [7, None, None]]
>>> f(L, 4)
[[1, 2, 3, 4], [5, 6, 7, None]]
>>> f(L, 7)
[[1, 2, 3, 4, 5, 6, 7]]


List comprehension
==================

>>> def f(L, c):
...     return [L[i:i+c] + [None]*(i+c-len(L)) for i in range(0,len(L),c)]
...
>>> f(L, 2)
[[1, 2], [3, 4], [5, 6], [7, None]]
>>> f(L, 3)
[[1, 2, 3], [4, 5, 6], [7, None, None]]
>>> f(L, 4)
[[1, 2, 3, 4], [5, 6, 7, None]]
>>> f(L, 7)
[[1, 2, 3, 4, 5, 6, 7]]


Recursive
=========

>>> def f(L, c):
...     return [L] if len(L)==c else [L+[None]*(c-len(L))] if len(L)<c else [L[:c]]+f(L[c:],c)
...
>>> def f(L, c):
...     return [L+[None]*(c-len(L))] if len(L)<=c else [L[:c]]+f(L[c:],c)
...
>>> f(L, 2)
[[1, 2], [3, 4], [5, 6], [7, None]]
>>> f(L, 3)
[[1, 2, 3], [4, 5, 6], [7, None, None]]
>>> f(L, 4)
[[1, 2, 3, 4], [5, 6, 7, None]]
>>> f(L, 7)
[[1, 2, 3, 4, 5, 6, 7]]


Lazy evaluation
===============

>>> def f(L, c):
...     if len(L) <= c:
...         yield L + [None] * (c - len(L))
...     else:
...         yield L[:c]
...         yield from f(L[c:], c)
>>> list(f(L, 2))
[[1, 2], [3, 4], [5, 6], [7, None]]
>>> list(f(L, 3))
[[1, 2, 3], [4, 5, 6], [7, None, None]]
>>> list(f(L, 4))
[[1, 2, 3, 4], [5, 6, 7, None]]
>>> list(f(L, 7))
[[1, 2, 3, 4, 5, 6, 7]]


Iteration magic
===============

>>> def f(L, c):
...     return list(zip(*[iter(L + ([] if len(L)%c==0 else [None]*(c-len(L)%c)))]*c))
...
>>> def f(L, c):
...     return list(zip(*[iter(L + ([None]*c)[:-(len(L)%c)])]*c))
...
>>> f(L, 2)
[(1, 2), (3, 4), (5, 6), (7, None)]
>>> f(L, 3)
[(1, 2, 3), (4, 5, 6), (7, None, None)]
>>> f(L, 4)
[(1, 2, 3, 4), (5, 6, 7, None)]
>>> f(L, 7)
[(1, 2, 3, 4, 5, 6, 7)]
"""