Iterate over a string 2 (or n) characters at a time in Python

Question

Earlier today I needed to iterate over a string 2 characters at a time for parsing a string formatted like "+c-R+D-E" (there are a few extra letters).

I ended up with this, which works, but it looks ugly. I ended up commenting what it was doing because it felt non-obvious. It almost seems pythonic, but not quite.

# Might not be exact, but you get the idea, use the step
# parameter of range() and slicing to grab 2 chars at a time
s = "+c-R+D-e"
for op, code in (s[i:i+2] for i in range(0, len(s), 2)):
  print op, code

Are there some better/cleaner ways to do this?

Answer 1

I don't know about cleaner, but there's another alternative:

for (op, code) in zip(s[0::2], s[1::2]):     print op, code 

A no-copy version:

from itertools import izip, islice for (op, code) in izip(islice(s, 0, None, 2), islice(s, 1, None, 2)):     print op, code 

Answer 2

Maybe this would be cleaner?

s = "+c-R+D-e"
for i in xrange(0, len(s), 2):
    op, code = s[i:i+2]
    print op, code

You could perhaps write a generator to do what you want, maybe that would be more pythonic :)