Issue w/ "With Open"

[snippsat]

Do I have to keep using the %s format, or is there an easier way?

%s is the old way to do string formatting,should not use it anymore.
The way now is to use f-Strings
Post a working code example now have guess,usually so is userinputs a string that have to be split it up.
If want to add comma can be done lke this.

userinputs = 'hello world 123'
userinputs = userinputs.split()
with open('file1.txt', 'a') as writer:
    writer.write(f"{','.join(userinputs)}\n")

If i run two times.

Output:
hello,world,123
hello,world,123