what's the difference in below two statements for string formatting?

Question

For any defined valriable 'e', what's the difference b/w:

logging.info("variable is : %s" % e) and loggin.info("variable is : ", e)

and when to use what? which one will be better for UTs ?

Answer 1

The second one will throw an exception if you have info logging enabled, you should use logging.info("variable is : %s", e), this way you only format the string if the message is going to be logged.