How to iterate through the alphabet?

Question

How can I iterate through the alphabet and have it continue past the letter Z? For example - a,b,c ... y,x,aa,ab,ac,ad

At the momenent this is my array

letters = [
           "a","b","c","d","e","f","g","h","i","k",
           "l","m","n","o","p","q","r","s","t","u",
           "v","w","x","y","z", "aa", "ab", "ac", "ad", "ae",
           "af", "ag", "ah", "ai", "aj", "ak", "al", "am", "an",
           "ao", "ap", "aq", "ar", "as", "at", "au", "av","aw", "ax", "ay",
           "az", "ba", "bb", "bc", "bd", "be", "bf", "bg", "bh", "bi",
           "bj", "bk", "bl", "bm", "bn", "bo", "bp", "bq", "br", "bs", "bt",
           "bu", "bv","bw", "bx", "by", "bz","ca","cb","cc","cd","ce",
           "cf","cg","ch","ci","cj","ck","cl","cm","cn","co","cp",
           "cq","cr","cs","ct","cu","cv","cw"]

but I want to make it created within a loop.

This is the general algorithm, in C#: http://stackoverflow.com/a/182924/2436175. The key is dividing by 26 converting the remainder into a letter at every step, until the division return 0. Use `%` (modulo) to get the remainder, `//` (floor division) to update the value for the next step. — Antonio, May 11 '17 at 14:35
@Antonio I think you'll agree that Uriel's second itertools-based solution is a lot cleaner than messing around with modular arithmetic. — PM 2Ring, May 11 '17 at 14:51
Do you really want them in a list? I think you'll find it much more convenient to have a generator that produces these strings for you. — PM 2Ring, May 11 '17 at 14:54
@PM2Ring I agree. Since in the meantime I had the solution ready, I posted it [here](http://stackoverflow.com/a/43918966/2436175). It shouldn't harm :) — Antonio, May 11 '17 at 14:56

Ajax1234 · Accepted Answer · 2017-05-11T14:48:38.083

7

You can try this:

import string

letters = list(string.ascii_lowercase)

letters.extend([i+b for i in letters for b in letters])

print letters

By using a double for loop, we iterate over the alphabet like we normally would, except we can put the iteration in list comprehension, to save space and be more pythonic.

edited May 11 '17 at 14:48

answered May 11 '17 at 14:39

Ajax1234

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Instead of just code dumping why not explain what your program does? Right now it's not really a complete answer. – MooingRawr May 11 '17 at 14:41
You are right. Please see my recent edit. – Ajax1234 May 11 '17 at 14:48
1

This assumes they want to stop at `zz`, a generic solution would be more useful, as suggested in the duplicate – Chris_Rands May 11 '17 at 14:49
1

Good point. However, I thought in the context of this problem and doing specifically what the OP had asked, this solution would suffice. – Ajax1234 May 11 '17 at 14:50

CIsForCookies · Answer 2 · 2017-05-11T14:44:25.063

5

since string.ascii_lowercase holds all of the lower-case letters, you can iterate through them in one loop (for 1-letter-string) or two (for 2-letters-string) and just add them to a list, like this:

import string
list = []
for c in string.ascii_lowercase: 
    list.append(c)

for c1 in string.ascii_lowercase:
    for c2 in string.ascii_lowercase:
        list.append(c1+c2)

print(list)

edited May 11 '17 at 14:44

answered May 11 '17 at 14:39

CIsForCookies

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Instead of just code dumping why not explain what your program does? Right now it's not really a complete answer. – MooingRawr May 11 '17 at 14:41

score 2 · Answer 3 · answered May 11 '17 at 14:41

string module would do the trick.

import string
alphabets=list(string.ascii_lowercase)
output=[] # output list
for a in alphabets:
     output.append(a)
for a in alphabets:
     for b in alphabets:
         output.append('%s%s' % (a,b))
print output

How to iterate through the alphabet?

3 Answers3