Python get range using start, end characters compatible with Excel

Question

How can I make this work with alpha_range(A, ZZ)?

right now it only work until Z

Code:

def alpha_range(start, stop):
    """ Returns chars between start char and stop char(A,D -> A,B,C,D).
    :param start: start char
    :param stop: stop char
    :return: list of chars
    """
    return [chr(x) for x in range(ord(start), ord(stop)+1)]

I don't understand the question. What is the output for `alpha_range('A', 'ZZ')` supposed to look like? — timgeb, Jan 21 '16 at 18:09
@timgeb: We want an alphabetical range that works like [the column labels in Excel](http://excelspreadsheet.net/images/yearlycalendar-004.jpg). — user2357112, Jan 21 '16 at 18:11
So your function should be able to also handle `alpha_range("BX", "XFD")`? — Tim Pietzcker, Jan 21 '16 at 18:13
Ok, what's the output for `alpha_range('A', 'BC')` supposed to look like? — timgeb, Jan 21 '16 at 18:14

nikihub · Answer 1 · 2016-01-21T18:41:09.287

3

You can easily make a bidirectional mapping between A-ZZ and numbers. This actually is pretty similar to a numeric system with different characters to represent the digits.

BASE = ord('Z') - ord('A') + 1

def to_number(str_input):
    res = 0
    for letter in str_input:
        res = res * BASE + ord(letter) - ord('A') + 1
    return res

def to_str(int_input):
    res = ''
    while int_input > 0:
        int_input -= 1
        res = res + chr(int_input % BASE + ord('A'))
        int_input //= BASE
    return res[::-1]

Now you can replace ord and chr with this functions.

edited Jan 21 '16 at 18:41

answered Jan 21 '16 at 18:16

nikihub

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1
5

1

Um, `to_number("AA")` returns `0`, should be `26`, `to_str(26)` returns `BA`. – Tim Pietzcker Jan 21 '16 at 18:22
You are right. Will fix the code. – nikihub Jan 21 '16 at 18:24
2

Great. To make it work with Python 3 as well, use `//=` instead of `/=`. – Tim Pietzcker Jan 21 '16 at 18:37
Then this is related: [Define a new numerical base in python (new charset)](http://stackoverflow.com/q/33240388/3821804) – GingerPlusPlus Jan 21 '16 at 18:48

Python get range using start, end characters compatible with Excel

1 Answers1