Custom functions – Řešení 
pi is global - it's not defined within the function and it's
accessible in the whole program.
area - Note there are two variables of that name! One is global
ant the other one is local inside the function
a - Note there are also two variables of that name. This was that catch:
a = a + 3 has no point. A value is assigned to the local
a, but the function ends right after that, and this
a is no
longer available, it will never be used.
b is only local - it's an argument for the
Toto je stránka lekce z kurzu, který probíhá nebo proběhl naživo s instruktorem.