Why is joining of strings still separated by a comma(separator) ?

Answer 1

I think you are talking about python. By the way we can use + also instead of ,

it will join the whole string

Answer 2

you need to split then join if you want remove the commas.
assuming you are talking about Python.
str = "a,b,c,d,e"
str = "".join(str.split(","))
str is now joined without comma