E10 - CSCI 141

Lecture 10 - Exercises

10A - Defining Functions

Which of the following is/are true of the print function?

It does not take inputs (arguments)
It does not return a value
It does not have any effects
Using it requires understanding the code that implements

You’ve seen the len function a couple times now. Describe its behavior in terms of its inputs, effects, and return value.

Input(s):
Effects:
Return value:

Which of the following programs will not cause an error when run?

def greet():
  print("Hi there!")
greet()

```
def greet():
  print("Hi there!")
```

greet()
def greet():
     print("Hi there!")

```
def greet:
  print("Hi there!")
greet()
```

10B - Passing inputs to functions

Consider the following program:

def h2m(hours, minutes):
  total_mins = 60 * hours + minutes
  return total_mins

arg1 = int(sys.argv[1])
arg2 = int(sys.argv[2])

print(h2m(arg1, arg2))

Suppose the program is run with two command line arguments and prints 80. If the first command line argument was 1, what must the second one have been?
Suppose the program is run with two command line arguments and prints 80. If you don’t know anything about either command line argument, how many possible pairs of numbers could have been given as command line arguments?

Consider the following program:

def pnmr(n, r):
    print(n % r, end=" ")

size = 7
rad = 3
for num in range(0,size):
    pnmr(num, rad)

How many numbers does this program print?
How many times does the program print the number 1?

B02 Peer Review

Before working on the Problems below, your group should peer review each group member’s submission for B02.py from Monday’s class. The Problems for today are also the same Problems for Friday’s class, so don’t rush through the peer review process - you will have plenty of time to work on the Problems.

For each group member, complete the following steps:

Create a copy of the B02 Peer Review: TEMPLATE slide, and put the group member’s name in place of TEMPLATE.

Paste your code in the box provided. Delete the instruction comments, if you haven’t already, to make the code fit.

As a group, review and test the code. For each of the rubric items below, decide whether the submission should receive credit or not. Fill in the box to the right of each rubric item.

Prints a message welcoming the user to Mount Baker Snowbank
Gets the two inputs from the command line arguments
For each week, the program prints a message reporting the current snowpack.
The program prompts the user to enter a command (1 point); and the prompt is repeated until a valid command (s, m, or c) is entered (1 point)
The “s” command works: prompts for a number and adds it to the current snowpack
The “m” command works: prompts for a number and subtracts it from the current snowpack
The “c” command works: snowpack remains unchanged and the program continues to the next week
An avalanche halves the snowpack if it’s greater than 100 inches after the week’s event
The final snowpack is printed in feet and inches.

Total up the score and enter it in the Total Score text box.

The author of the code should now decide whether they would like to work on fixing errors or adding missing features as a group in class, or individually outside fo class.

Problems

Write a function parrot that takes one string argument (s) and one integer argument (n) and prints that string n times with a space in between; at the end, the function should print a single newline. Examples:

>>> parrot("hello!", 3)
hello! hello! hello!
>>> parrot("click", 5)
click click click click click
>>>

Write a function rectangle_area that takes two numbers height and width and returns the area of a height-by-width rectangle. Recall that a $h \times w$ rectangle has area h*w .

Write a function circle_area that takes one number radius and returns the area of a circle with that radius. Recall that a circle with radius has area $\pi r^2$ .

Write a function get_float that takes a string, prints that string, then prompts a user for a floating-point number and returns their input converted to a float.

>>> get_float("Enter a radius: ")
 Enter a radius: 4
4.0

(Note: in the above, 4 is entered by the user, and 4.0 is printed on the Thonny shell in dark blue, showing the return value of the call to get_float)

Use the functions from the prior three problems to create a geometry game as follows. The program takes two command line arguments specifying the width and height of a rectangle. Then, it repeatedly prompts the user for a radius. For each radius provided, print a message saying whether the circle with the given radius has area greater than, smaller than, or equal to the rectangle’s. If the user enters a negative number, the program should terminate.

Write a function print_banner that takes a string argument and prints that string, surrounded by a rectangle of # symbols. Here are some examples of how the function might be called:

>>> print_banner("Hello!")
########
#Hello!#
########
>>> print_banner("You enter a room with two doors on the opposite wall.")
#######################################################
#You enter a room with two doors on the opposite wall.#
#######################################################
>>>

Assume there are no newline characters (\n) in the string you’re given, and that the string can be printed on one line.

Write a function add_banner function that does the same thing as print_banner, except that it returns the string as a banner instead of printing it.

Note: It came to my attention that you don’t have the tools you need to solve this one! After Week 6 you will, but don’t worry if you aren’t able to solve this yet.

Modify your add_banner function to implement text wrapping, so that a string longer than 80 characters will be broken into multiple lines. You can still assume the string does not contain any newlines. An example might look something like the following:

>>> print_banner("Modify your print_banner to implement text wrapping so that a string longer than 80 characters will be broken into multiple lines.")
##################################################################################    
#Modify your print_banner to implement text wrapping so that a string longer than#
#80 characters will be broken into multiple lines.                               #
##################################################################################
>>>