interleave_list_lexicographically.py

import string

input_file = open('massachusetts_municipalities.txt', 'r')
list_entries = {}

for line in input_file:
    if line[0] not in list_entries:
        list_entries[line[0]] = []
    list_entries[line[0]].append(line.strip())
output_file = open('interleaved_list.txt', 'w')
while(len(list_entries) > 0):
    for key in string.ascii_uppercase:
        if key in list_entries and len(list_entries[key]) == 0:
            list_entries.pop(key,None)
        if key in list_entries:
            output_file.write( list_entries[key].pop(0) + '\n')

output_file.close()    

massachusetts_municipalities.txt

Abington
Acton
Acushnet
Adams
Agawam
Alford
Amesbury
Amherst
Andover
Aquinnah
Arlington
Ashburnham
Ashby
Ashfield
Ashland
Athol
Attleboro
Auburn
Avon
Ayer
Barnstable
Barre
Becket
Bedford
Belchertown
Bellingham
Belmont
Berkley
Berlin
Bernardston
Beverly
Billerica
Blackstone
Blandford
Bolton
Boston
Bourne
Boxborough
Boxford
Boylston
Braintree
Brewster
Bridgewater
Brimfield
Brockton
Brookfield
Brookline
Buckland
Burlington
Cambridge
Canton
Carlisle
Carver
Charlemont
Charlton
Chatham
Chelmsford
Chelsea
Cheshire
Chester
Chesterfield
Chicopee
Chilmark
Clarksburg
Clinton
Cohasset
Colrain
Concord
Conway
Cummington
Dalton
Danvers
Dartmouth
Dedham
Deerfield
Dennis
Dighton
Douglas
Dover
Dracut
Dudley
Dunstable
Duxbury
East Bridgewater
East Brookfield
East Longmeadow
Eastham
Easthampton
Easton
Edgartown
Egremont
Erving
Essex
Everett
Fairhaven
Fall River
Falmouth
Fitchburg
Florida
Foxborough
Framingham
Franklin
Freetown
Gardner
Georgetown
Gill
Gloucester
Goshen
Gosnold
Grafton
Granby
Granville
Great Barrington
Greenfield
Groton
Groveland
Hadley
Halifax
Hamilton
Hampden
Hancock
Hanover
Hanson
Hardwick
Harvard
Harwich
Hatfield
Haverhill
Hawley
Heath
Hingham
Hinsdale
Holbrook
Holden
Holland
Holliston
Holyoke
Hopedale
Hopkinton
Hubbardston
Hudson
Hull
Huntington
Ipswich
Kingston
Lakeville
Lancaster
Lanesborough
Lawrence
Lee
Leicester
Lenox
Leominster
Leverett
Lexington
Leyden
Lincoln
Littleton
Longmeadow
Lowell
Ludlow
Lunenburg
Lynn
Lynnfield
Malden
Manchester-by-the-Sea
Mansfield
Marblehead
Marion
Marlborough
Marshfield
Mashpee
Mattapoisett
Maynard
Medfield
Medford
Medway
Melrose
Mendon
Merrimac
Methuen
Middleborough
Middlefield
Middleton
Milford
Millbury
Millis
Millville
Milton
Monroe
Monson
Montague
Monterey
Montgomery
Mount Washington
Nahant
Nantucket
Natick
Needham
New Ashford
New Bedford
New Braintree
New Marlborough
New Salem
Newbury
Newburyport
Newton
Norfolk
North Adams
North Andover
North Attleborough
North Brookfield
North Reading
Northampton
Northborough
Northbridge
Northfield
Norton
Norwell
Norwood
Oak Bluffs
Oakham
Orange
Orleans
Otis
Oxford
Palmer
Paxton
Peabody
Pelham
Pembroke
Pepperell
Peru
Petersham
Phillipston
Pittsfield
Plainfield
Plainville
Plymouth
Plympton
Princeton
Provincetown
Quincy
Randolph
Raynham
Reading
Rehoboth
Revere
Richmond
Rochester
Rockland
Rockport
Rowe
Rowley
Royalston
Russell
Rutland
Salem
Salisbury
Sandisfield
Sandwich
Saugus
Savoy
Scituate
Seekonk
Sharon
Sheffield
Shelburne
Sherborn
Shirley
Shrewsbury
Shutesbury
Somerset
Somerville
South Hadley
Southampton
Southborough
Southbridge
Southwick
Spencer
Springfield
Sterling
Stockbridge
Stoneham
Stoughton
Stow
Sturbridge
Sudbury
Sunderland
Sutton
Swampscott
Swansea
Taunton
Templeton
Tewksbury
Tisbury
Tolland
Topsfield
Townsend
Truro
Tyngsborough
Tyringham
Upton
Uxbridge
Wakefield
Wales
Walpole
Waltham
Ware
Wareham
Warren
Warwick
Washington
Watertown
Wayland
Webster
Wellesley
Wellfleet
Wendell
Wenham
West Boylston
West Bridgewater
West Brookfield
West Newbury
West Springfield
West Stockbridge
West Tisbury
Westborough
Westfield
Westford
Westhampton
Westminster
Weston
Westport
Westwood
Weymouth
Whately
Whitman
Wilbraham
Williamsburg
Williamstown
Wilmington
Winchendon
Winchester
Windsor
Winthrop
Woburn
Worcester
Worthington
Wrentham
Yarmouth