unnecessary utility

[GreatBahram]

It seems you don't need utils at all.
You can use some kind of comprehension to make the code even much more readable and independent.

return ''.join(
    dic.get(char, char) # maybe dic is not a good name though
    for char in string
)

persiantools/persiantools/digits.py

Line 28 in a88112b

return utils.replace(string, dic)