"""Chapter 2.7, exercise 7.

Write a generator that yields an infinite sequence of alpha-numeric identifiers,
starting with a1 through z1, then a2 through z2, and so on.

"""
import string

def generate_identifier():
    num = 1
    while True:
        for c in string.lowercase:
            yield c + str(num)
        num += 1


if __name__ == '__main__':
    try:
        for name in generate_identifier():
            print name
    except KeyboardInterrupt:
        print "Control-C interrupt"