Question

my_list = ['apple', 'pear', 'orange', 'raspberry']

# I know that I'm always looking for pear.
print 'pear' in my_list # prints True

# I want to be able to get a key by its value.
pear_key = my_list['pear'].key # should be 1

# Print the next item in the list.
print my_list[pear_key + 1] # should print orange

I know that pear will always be an item in my list (not the position though), and I’m looking for a way to get the value of the next item in that list, either by getting the current key by knowing its value and advancing it by one (like I did in the example above) or by using something like my_list.next.

Answer 1

try:
    pos = my_list.index('pear')
    print my_list[pos + 1]
    # orange
except IndexError as e:
    pass # original value didn't exist or was end of list, so what's +1 mean?

You could of course pre-cache it, by using (think it’s probably the itertools pair recipe)

from itertools import tee
fst, snd = tee(iter(my_list))
next(snd, None)
d = dict(zip(fst, snd))

But then you lose the fact of whether it was in the original list, or just didn’t have a logical next value.