In Python is very simple

Example

age = int(19)
txt = str("Hello my name is Beno, i'am {} years old")
print(txt.format(age))

Added const for the char* r

That's just a formatting preference. What's I think is a bad formatting preference is putting anything after a scope-closing } on the same line.

Just a minor Feedback:
if you're using the curlybrackets, then put them in the next row so the code is simpler to read.

char fanis(char r, int k) {
for (; *r; *r++)
*r = k + *r;
return r;
}