What is the output of the following Python code?a = [1, 2, 3] b = a a = a + [4] print(b, len(a))

a = [1, 2, 3]
b = a
a = a + [4]
print(b, len(a))

Explanation

a + [4] builds a new list and rebinds a, so b still refers to the original [1, 2, 3] while len(a) is 4.