Start index for iterating Python list

Question

What is the best way to set a start index when iterating a list in Python. For example, I have a list of the days of the week - Sunday, Monday, Tuesday, ... Saturday - but I

Answer 1

You can use slicing:

for item in some_list[2:]:
    # do stuff

This will start at the third element and iterate to the end.

Answer 2

Here's a rotation generator which doesn't need to make a warped copy of the input sequence ... may be useful if the input sequence is much larger than 7 items.

>>> def rotated_sequence(seq, start_index):
...     n = len(seq)
...     for i in xrange(n):
...         yield seq[(i + start_index) % n]
...
>>> s = 'su m tu w th f sa'.split()
>>> list(rotated_sequence(s, s.index('m')))
['m', 'tu', 'w', 'th', 'f', 'sa', 'su']
>>>