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).

Answer 1

from itertools import izip_longest
def grouper(iterable, n, fillvalue=None):
    args = [iter(iterable)] * n
    return izip_longest(*args, fillvalue=fillvalue)
def main():
    s = "+c-R+D-e"
    for item in grouper(s, 2):
        print ' '.join(item)
if __name__ == "__main__":
    main()
##output
##+ c
##- R
##+ D
##- e

izip_longest requires Python 2.6( or higher). If on Python 2.4 or 2.5, use the definition for izip_longest from the document or change the grouper function to:

from itertools import izip, chain, repeat
def grouper(iterable, n, padvalue=None):
    return izip(*[chain(iterable, repeat(padvalue, n-1))]*n)