Python character function, where is the "Z"?

Question

I'm trying to convert numbers to excel column letters.

Code:

def num2col(num):
    letters = ''
    while num:
        mod = num % 26
        num = num // 26
        letters += chr(mod + 64)
    return ''.join(reversed(letters))

print num2col(25), num2col(26), num2col(27)    
print num2col(51), num2col(52), num2col(53)
print num2col(77), num2col(78), num2col(79)

Desired output:

Y Z AA
AY AZ BA
BY BZ CA

Actual output:

Y A@ AA
AY B@ BA
BY C@ CA

Try `letters += chr(mod + 65)` instead of `letters += chr(mod + 64)` — inspectorG4dget, Aug 04 '14 at 04:28
Try `mod = mod if mod > 0 else 26` right after `mod = num % 26` (and forget the last thing I said) — inspectorG4dget, Aug 04 '14 at 04:32
If you're trying to convert numbers to Excel column labels, shouldn't the one after `Y` be `Z`? — user2357112, Aug 04 '14 at 04:40
26 mod 26 is 0. ASCII 64 is @. If A=1, you're not going to get a Z from your loop. Try 65 + ((num - 1) % 26) — Art Taylor, Aug 04 '14 at 04:46

falsetru · Accepted Answer · 2014-08-04T04:42:58.250

4

def num2col(num):
    letters = ''
    while num:
        num, mod = divmod(num-1, 26)
        letters += chr(mod + 65)      # 65 == ord('A')
    return ''.join(reversed(letters))

print num2col(25), num2col(26), num2col(27)    
print num2col(51), num2col(52), num2col(53)
print num2col(77), num2col(78), num2col(79)

output:

Y Z AA
AY AZ BA
BY BZ CA

edited Aug 04 '14 at 04:42

answered Aug 04 '14 at 04:33

falsetru

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Thanks for the fix. I've used my original code for years, some how by luck column letter ending in 'Z' never showed up... til now... – jason Aug 04 '14 at 04:50

Python character function, where is the "Z"?

1 Answers1