speedup function coordinate_to_string

[sdementen]

as the function is used a lot when saving a Workbook, I have simplified it by using a lookup logic (mapping of column letters to column coordinates and vice versa) => 3x faster
I have also updated the function string_to_coordinate in the same spirit (avoid modulo calculation and use lookup)

[kevmo314]

Thanks! Mostly looks good, just a question about populating the lookup table.

[kevmo314]

Awesome, thanks again for the change!

[sdementen]

I wonder if the two definitions A and Z in Range are still needed or if they were only used for the functions that have been changed

class Range(object):
    A = ord("A")
    Z = ord("Z")

[kevmo314]

Good catch, I think they can be removed. I don't foresee anyone passing Range.A or Range.Z to any functions meaningfully.

[sdementen]

Good catch, I think they can be removed. I don't foresee anyone passing Range.A or Range.Z to any functions meaningfully.

Should I push again the branch with the changes? Or do you take this change in another PR?

[kevmo314]

Already submitted the change :)