Building strings in a loop

A helper variable doesn't have to hold a number. A string can grow in a loop too: start with the empty string "" and add to it with +=, which joins strings just as + does:

stars = ""
count = 0
while True:
    stars += "*"
    count += 1
    if count == 5:
        break
print(stars)

*****

Each iteration adds one * to the end of stars, and the whole string is printed once, after the loop.

Collecting input

In the same way, a program can collect what the user types:

guests = ""
while True:
    name = input("Guest (done to finish): ")
    if name == "done":
        break
    guests += name
print("Guests: " + guests)

Ada
Alan
Grace
done

Guest (done to finish): Ada
Guest (done to finish): Alan
Guest (done to finish): Grace
Guest (done to finish): done
Guests: AdaAlanGrace

Almost: += joins the strings exactly as they are, so the names run together. They need a comma and a space between them, but not before the first name, and not after the last one either. So add the separator in front of each name, except the first:

guests = ""
while True:
    name = input("Guest (done to finish): ")
    if name == "done":
        break
    if guests == "":
        guests = name
    else:
        guests += ", " + name
print("Guests: " + guests)

Ada
Alan
Grace
done

Guest (done to finish): Ada
Guest (done to finish): Alan
Guest (done to finish): Grace
Guest (done to finish): done
Guests: Ada, Alan, Grace

guests == "" is true only for the first name, while nothing has been added yet.

Numbers into the string

+ joins only strings, so a number must be converted with str before it's added:

>>> row = ""
>>> row += str(1) + " "
>>> row += str(2) + " "
>>> row
'1 2 '

Without str, Python stops with the TypeError you saw earlier: can only concatenate str (not "int") to str.