Subprograms Practice

These questions follow Subprograms and Modules. A function is a recipe with a name — write it once, use it everywhere.

Questions

1. Predict the output — how many lines, and in what order?

   def greet(name):
       print("Hello, " + name + "!")
   greet("Ada")
   greet("Grace")

2. Predict the output. Trace the value all the way through.

   def double(n):
       return n * 2
   print(double(5) + 1)

3. Inside a function, how do print and return differ? One sentence each.
4. Find the bug. This prints 5 — then crashes. Explain both.

   def add(a, b):
       print(a + b)
   total = add(2, 3) + 10

5. Write a function area(width, height) that returns a rectangle’s area, then one line using it for a 3 by 5 rectangle.
6. Challenge. Write is_teen(age) returning True or False, then use it in an if to decide on a movie ticket price.
7. External modules. Using Python’s built-in random module, write a function roll_d20() that imports random, generates a random integer from 1 to 20 using random.randint(), and returns it. Then write one line calling roll_d20() and printing the result.
8. Mathematical libraries. Write a function distance(x1, y1, x2, y2) that uses import math and math.sqrt((x2 - x1)**2 + (y2 - y1)**2) to calculate and return the straight-line distance between two 2D points. Explain why borrowing standard libraries makes your code more reliable.

Answers

Answer 1

Two lines: Hello, Ada! then Hello, Grace!. The def block runs nothing by itself — each call runs it, in the order called.

Answer 2

double(5) hands back 10, then 10 + 1 is 11, so 11 prints. The return value flows to wherever the call sits.

Answer 3

print shows a value to the human and keeps nothing. return hands a value back to the program, for the next step to use.

Answer 4

add prints its answer but returns nothing, so add(2, 3) is None — and None + 10 is a TypeError. Use return a + b.

Answer 5

def area(width, height): with return width * height beneath — then print(area(3, 5)), which shows 15.

Answer 6

def is_teen(age): then return age >= 13 and age <= 19 — the comparison already is True or False. Then if is_teen(15): discount price, else: full price.

Answer 7

import random
 
def roll_d20():
    return random.randint(1, 20)
 
print("Rolled:", roll_d20())

Using an existing library module (random) provides robust, tested pseudo-random number generation without having to implement complex mathematical random generators from scratch.

Answer 8

import math
 
def distance(x1, y1, x2, y2):
    return math.sqrt((x2 - x1)**2 + (y2 - y1)**2)
 
print("Distance:", distance(0, 0, 3, 4))

Built-in modules like math are optimized in C, thoroughly tested, and handle edge cases (like precision and domain errors) accurately.

Curriculum connection

C3.3

write subprograms, and use existing subprograms, to complete program components

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C3.4

write programs that make use of external or add-on modules or libraries

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