Question

Given the following Python code:

def avg(a):
  if len(a):
    return sum(a) / len(a)

What is the language defined behavior of avg when the length of a is zero or is its behavior unspecified by the language and thus should not be counted upon in Python code?

Answer 1

The default return value is None.

From the documentation on Calls:

A call always returns some value, possibly None, unless it raises an exception. How this value is computed depends on the type of the callable object.