To create a single string from a list of multiple strings, you can use any of the options depending on the separator you want between the strings. Here’s a breakdown:

''.join(my_list) – This joins the list items into a single string with no separator between them.
', '.join(my_list) – This joins the list items into a single string with a comma and a space as separators.
' '.join(my_list) – This joins the list items into a single string with a space as the separator.
'-'.join(my_list) – This joins the list items into a single string with a hyphen as the separator.

To convert a string into a number in Python, you can use the built-in functions int() or float(), depending on whether you want an integer or a floating-point number. The int() function is used to convert a string into an integer, while float() is used to convert a string into a float number. str() converts other data types to string and list() converts other types to list.