Iterating over every two elements in a list [duplicate]

How do I make a for loop or a list comprehension so that every iteration gives me two elements?

l = [1,2,3,4,5,6]

for i,k in ???:
    print str(i), '+', str(k), '=', str(i+k)

Output:

1+2=3
3+4=7
5+6=11