that is necessary, but not sufficient, for the program to be correct, aka “reliable“.
Not in python it isn't.
I was surprised the first time I learned that Python will actually refuse to compile:
def fibonacci(n):
return n
because it knows that the Fibonacci sequence doesn't work that way. It's a fantastic language.
If it’s valid utf8 I consider it ready for production.
Decades of optimizing compilers, static analyzers, and software engineering practices when the solution to quality was right under our noses all along.