Convert list to string (CSV type)

Consider the code snippet below:

lis = [1, 3, 5, 6, 2, 1, 3]
print (lis)
print(type(lis))

Output:

[1, 3, 5, 6, 2, 1, 3]
<class 'list'>

I want the similiar output, obviously without the square braces, but the datatype has to be string for some further operations.

Can anyone help me on this ?