Global vs Local Variables

Write on the IDLE (python editor) the following programs, run each one of them and reply for each one the questions/requests below:

Program #1

Why do you get an error in line 8?

Reply below:

Program #2

Why do you get 1 from line 8?

Reply below:

Program #3

Why do you get 3 from line 10?

Reply below:

Program #4

In this program, f1 should have read-only access to global variables since it does not take write access to any global variable. Therefore we should be able to get an output from instruction line 4. However, python returns an error for line 4, informing that a variable is being used before its assignment (line 5). Such an error is because line 5 creates a local variable with the same name as the global variable, and we cannot access that local variable before the assignment.

Add a screenshot (entire screen, no cuts) of this run-output for this program.

Writing a benchmark program

The following code uses the module time to do a benchmark. A benchmark is a program that runs several instructions or repeated instructions to measure the time required. Depending on the employed time, we can decide if a computer is faster than another or if a code is faster than another. Write this program in the IDLE (python editor) and run it several times (5 times or more, press the function key F5 to run a program).

The code executes the same operation several times (10000) in two ways, one using a direct calculation (line 9: ris=a*b*c) and one using a function to a multiplication between two numbers used twice (line 15: ris=fun(fun(a, b), c)).

Moreover, the program takes track of the time employed to run 10000 times a direct operation on t_passed1 and the time required to call 10000 the function doing the same calculation on t_passed2.

Finally, the program compares those passed times and decides which one is the faster implementation.

Running several times such that program, you will see that one of the two implementations (direct operation vs function) is generally faster. However, the result you can obtain from a benchmark is firmly dependent on the simultaneous jobs carried by a computer at that moment. For such a reason, you should run the code several times to decide on a response (or disable any other program in the background).

Now say what affirmations apply to direct operations or to call of functions:

Direct operations	Functions	Affirmation
		are faster
		They require less program memory since we can reuse code
		They are easy to read and understand because they have less code read.
		They are easy to maintain (modify, improve, correct) because they have less code.

Provide the screenshot of the run-output (entire screen, no cuts).