postcode_generator.py

from random import choice, shuffle
import string

outwardcode_area_choices = ['LS', 'EN', 'BD']
outwardcode_district_choices = xrange(1,20)
inwardcode_sector_choices = string.digits
inwardcode_alphabet = list('ABDEFGHJLNPQRSTUWXYZ')

def gen_postcode():
    shuffle(inwardcode_alphabet)
    values = {
        "outwardcode_area": choice(outwardcode_area_choices),
        "outwardcode_district": choice(outwardcode_district_choices),
        "inwardcode_sector": choice(inwardcode_sector_choices),
        "inwardcode_unit": ''.join(inwardcode_alphabet[:2])
    }
    output_spec = "{outwardcode_area}{outwardcode_district}" + \
        " {inwardcode_sector}{inwardcode_unit}"
    return output_spec.format(**values)

# generate one
print gen_postcode()
# generate 100
print '\n'.join([gen_postcode() for _ in xrange(0,100)])