4.1. Indentation and block structuring

Python differs from most other programming languages because it uses whitespace and indentation to determine block structure (that is, to determine what constitutes the body of a loop, the else clause of a conditional, and so on). Most languages use braces of some sort to do this. Here is C code that calculates the factorial of 9, leaving the result in the variable r:

/* This is C code  */
int n, r;
n = 9;
r = 1;
while (n > 0) {
    r *= n;
    n--;
}