sys.stdout.write() Acting different in interactive mode

I have the code :

import sys
import time

for i in range(10):
    sys.stdout.write("\r Loading: {}".format(i))
    sys.stdout.flush()
    time.sleep(0.5)

which works perfectly when I run python3 dynamic_print.py, but when I fire the up the interactive interpreter by typing python3 and copy and run the above code into it, I get the output :

 Loading: 012
 Loading: 112
 Loading: 212
 Loading: 312
 Loading: 412
 Loading: 512
 Loading: 612
 Loading: 712
 Loading: 812
 Loading: 912

The last two digits 12, are updated every time I run it (it was 11 when I ran it the last time). Why does it act differently and how to mitigate this?

12 is the return value of write, i.e. the number of characters written. which in interactive mode is printed out, followed by a line feed

to fix this you could either indicate to the interpreter that you're not interested in this value (e.g. using _ = stdout.write(s)) or you could put everything into a function and hence keep it away from the REPL

I'd suggest doing the latter, e.g. something like:

def looper(n):
    for i in range(n):
        sys.stdout.write("\r Loading: {}".format(i))
        sys.stdout.flush()
        time.sleep(0.5)
    sys.stdout.write("\n")

then invoke as looper(10)