Appending to a text string

[snippsat]

I tried your code and I got the following error message. I'm using Python 2.7:

Stop using Python 2.7 is not supported anymore,will not be maintained at all past 2020.
f-string that i use was new in Python 3.6 -->

For python 2 use .format

f = open("password.txt", "r")
s = f.read()
f_out = open("password2.txt", "wt")

for count in range(1900,2021):
    f_out.write('{}{}\n'.format(s, count))
f_out.close()

Output:
password1900
password1901
password1902
password1903
password1904
password1905
.....