Question

I have one question because I can not find a solution for my problem.

gen is a generator (result of difflib.Differ.compare()):

normally by iterating over gen I can read each line. The problem is that on each iteration I need to read the current line and the two next lines.

Example (normal output by iterating line by line):

iteration 1:
    line = 'a'
iteration 2:
    line = 'b'
iteration 3:
    line = 'c'
iteration 4:
    line = 'd'
iteration 5:
    line = 'e'
iteration 6:
    line = 'f'
iteration 7: 
    line = 'g'

but in my case I need to get this:

iteration 1:
    line = 'a'
    next1 = 'b'
    next2 = 'c'
iteration 2:
    line = 'b'
    next1 = 'c'
    next2 = 'd'
iteration 3:
    line = 'c'
    next1 = 'd'
    next2 = 'e'
iteration 4:
    line = 'd'
    next1 = 'e'
    next2 = 'f'
iteration 5:
    line = 'e'
    next1 = 'f'
    next2 = 'g'
iteration 6:
    line = 'f'
    next1 = 'g'
    next2 = None
iteration 7: 
    line = 'g'
    next1 = None
    next2 = None

I was trying to play with gen.send(), itertools.islice(), but I can not find the proper solution. I don’t want to convert this generator into a list (then I could read next1 as gen[i + 1], next2 as gen[i + 2], but this is totally inefficient when the diff output is large.

Answer 1

Try keeping temporary variables.

line = iterator.next()
next1 = iterator.next()

for next2 in iterator:
    #do stuff
    line = next1
    next1 = next2