Questions

Conceptual

1. Every if statement must be followed by a paired else branch. (T/F)

2. Lines contained in an else branch in Python do not have to be indented. (T/F)

3. You can name a variable else in your program without Python confusing your variable’s name and the else keyword. (If you are unsure, this is a good one to try yourself!) (T/F)

4. All subquestions of this problem will refer to this code snippet:

    x: int = int(input("Pick a number: "))
    y: int = 10
    z: int = 2
    x = x - 1
    if x < 10:
        print("A")
    else:
        if (x % z) == 0:
            print ("B")
    if x == (y + z):
        print("C")
    else: 
        print("D")

For the following subquestions, answer with a valid input value for x that would cause the given letter to print. It is OK for your input to cause other letters to print as well. If there is no such value, write “Unreachable”.

4.1 A

4.2 B

4.3 C

4.4 D

Now, answer with a valid input value for x that would cause the exact given letter(s) to print (no other letters). If there is no such value, write “Unreachable”.
4.5

A
C

4.6

B
C

4.7

C

4.8

D

5. Write the format of a conditional using the following: You might not need to use all and can use any multiple times: if, else, ==, <condition>, False, True, <do something>.

6. Write the format of a conditional using the following: You might not need to use all and can use any multiple times: while, <condition>, ==, False, True, <do something>.

7. What does the condition of a conditional have to evaluate to in order to enter its block?

8. What happens when a return statement is encountered?

All subquestions of this problem will refer to this pseudo code snippet:

    if <condition1>:
        <do_something>
    elif <condition2>:
        <do_something>
    else:
        <do_something>

9. From the general format of a conditional with an elif block, what needs to be True and/or False in order for the elif block to evaluate?

10. Is <condition1> not being met the same as having if <condition1> == False:?

All subquestions of this problem will refer to this code snippet:

    def main() -> None: 
        x: str = "x"
        y: str = "y"
        z: str = x
        y = x
        x = "y"

        if not(x != y and x != "y"):
            print(f"x: {x}")
        else:
            print("'if' condition not met.")

    main()

11. What is the condition in this code?

12. What does the condition evaluate to? (Don’t do it in your head, draw a memory diagram!)

13. What values should x, y, and/or z have to be assigned to in order for the else block to run?

14. What other values can x, y, and/or z be assigned in order for the if block to run?

solutions

Solutions

Conceptual Questions - Solutions

1. F

2. F

3. F

4. 4.1 Any value < 11

   4.2 Any value >= 11 and odd. (Since x % z == 0 must be True and z is 2, this means x - 1 must be even.)

   4.3 13

   4.4 Any value != 13

   4.5 Unreachable

   4.6 13

   4.7 Unreachable

   4.8 Any value >= 11 and even

    if <condition> == True:
        <do_something>
    else:
        <do_something>

OR

    if <condition>:
        <do_something>
    else:
        <do_something>

    while <condition> == True:
        <do_something>

OR

    while <condition>:
        <do_something>

7. The condition must always evaluate to True.

8. The return value is recorded in memory and the function is immediately exited.

9. <condition1> must not be met (condition should evaluate to False) AND <condition2> must be met (condition should evaluate to True).

10. In this case, yes. If we had something like this:

if ("hello" == "hello") == False:

the <condition> in this case would be everything in between the if and the :. In the pseudo-code, we are separating the <condition> to be separate from the rest (== False), while in real code the condition is always everything after the if and before the :.

11. not(x != y and x != "y")

12. The condition evaluates to True.

13. To ensure the else block runs in the given code, the condition x != y and x != "y" must be true. This means x should be different from y and x should also be different from the string "y". For example, setting x = "a" and y = "b" will satisfy this condition, making the else block execute.

14. To make the if block run, the condition not(x != y and x != "y") must be true, which happens when x is either the same as y or the same as "y", or both. In the original code where x = "y", y = "x", and z = "x", the if block runs as not(x != y and x != "y") evaluates to true.