can only concatenate str (not "set") to str

This error occurs when you try to concatenate a set object with a string object using the + operator. In Python, the + operator is used for concatenation of two strings, but it cannot be used to concatenate a set object with a string object because they are of different types.

To resolve this error, you need to convert the set object to a string object before concatenating it with the string. You can do this using the str() function. Here is an example:

set_obj = {'a', 'b', 'c'}
string_obj = 'Hello'

# convert set to string
set_str = str(set_obj)

# concatenate string and set string
result = string_obj + set_str

print(result)

Output:

Hello{'a', 'b', 'c'}

In this example, we first convert the set object to a string using the str() function, and then concatenate it with the string object using the + operator. The output is a concatenated string of both objects.