Adding a comma to a string

Question

Good personal and possible to add comma in an example string:

a = '1234567890abcdefghijklmnopqrstuvwxyz_'

for her to stay like this a = 1,2,3,4,5,6,7....

Answer 1

Do the following:

lst = list(a) // transforma sua string em lista 
txt = ",".join(lst) // coloca vírgula entre as letras

Note that this can be done in just one step:

a = ",".join(a)