How to parameterize a login page using Sikuli IDE

put your 20 logins into a textfile like this
name password
name password
...

in your script:

logins = []
f = open("path to your textile")
for line in f.readlines():
    (n, p) = line.strip().split()
    logins.append([n.strip(), p.strip()]}

now you have a list of 20 name-password-pairs, that you can use to fill in.

if your names and/or passwords contain whitespace characters, the you have to use a unique separator, that does not show up in the names or password (e.g. | )

a line in your textfile:
name | password

and the relevant script line:
    (n, p) = line.strip().split("|")