[Python] Is the right-hand side of an assignment always evaluated before the assignment?

Here is a code snippet.

x = {}
x[1] = len(x)

print x
{1: 0}


Is this well defined? That is, could x == {1: 1} instead?

Because I remember that an equivalent program in C++ '98 (if we use std::map) has undefined behaviour. The output of the program was different when compiled with VS compiler and G++.

Continue reading...