13.2 The scope of a variable

A variable defined in one part of a program does not need to be known in other parts. All program units to which a certain variable is known are called the scope of that variable. We'll first give an example. Let's consider the two nested functions:

e = 3
def my_function(in1):
    a = 2 * e
    b = 3
    in1 = 5
    def other_function():
       c = a
       d = e
       return dir()
    print(f"""
          my_function's namespace: {dir()} 
          other_function's namespace: {other_function()}
          """)
    return a

The execution of my_function(3) results in:

my_function's namespace: ['a', 'b', 'in1', 'other_function'] 
other_function's namespace: ['a', 'c', 'd']

The variable e is in the namespace of the program unit that encloses the function my_function. The variable...