In this function y initially has no value, but a call to foo() gives no error. Why?

[Pedroski55]

Thanks a lot!

I'll let this sink in for a while, maybe I'll have a "Eureka!"

All I know is, try calling a function that requires 1 or more parameters, but don't pass a parameter, and you get this:

>>> foo()
Traceback (most recent call last):
File "<pyshell#2>", line 1, in <module>
foo()
TypeError: foo() missing 1 required positional argument: 'x'

Apparently, if the function is inside another function, you're OK.

Don't know when I might need this fuctionality, but I will remember it!