6.10 Scope of variables and functions

• A variable or function object is only visible to part of a program, known as the object's scope.
• When a variable is created inside a function, the variable's scope is limited to inside that function.
  • Because a variable's name does not exist until bound to an object, the variable's scope is actually limited to after the first assignment of the variable until the end of the function.

The function's variables total_inches and centimeters are invisible to the code outside of the function and cannot be used

• Such variables defined inside a function are called local variables.

Global variables

• In contrast, a variable defined outside of a function is called a global variable.
• A global variable's scope extends from assignment to the end of the file and can be accessed inside of functions.
• A global statement must be used to change the value of a global variable inside of a function.

• To be able to call a function, the interpreter must have already evaluated the function definition (thus binding the function name to a function object).