[Python-ideas] Should Python have user-defined constants?

Hey guys I am thinking of perhaps writing a PEP to introduce user-defined constants to Python. Something along the lines of Swift’s “let” syntax (e.g. “let pi = 3.14”). Do you guys think it would be a good idea? Why or why not? Do you think there’s a better way to do it? I’d like to know what others think about this idea before making any formal submission (I’ve already posted this same question on python-list, but I just wanted to gauge opinion here too).