Functions

Write a function add(i, j) that returns the sum of two numbers. Replace the inline sum in the cell with a call to it. Put the function at the top of the cell, so it exists before the first call. Run the cell.

Add 7.0 and 2.0 : 9.0

def add(i, j):
    return i + j


f1 = 7.0
f2 = 2.0

addresult = add(f1, f2)
print(f"Add {f1} and {f2} : {addresult}")

Write subtract, multiply and divide the same way, and replace the other three inline calculations with calls to them. The output has to be the same four lines as before.

Add 7.0 and 2.0 : 9.0
Subtract 2.0 from 7.0 : 5.0
Multiply 7.0 by 2.0 : 14.0
Divide 7.0 by 2.0 : 3.5

def subtract(i, j):
    return i - j


def multiply(i, j):
    return i * j


def divide(i, j):
    return i / j


subtractresult = subtract(f1, f2)
print(f"Subtract {f2} from {f1} : {subtractresult}")
multiplyresult = multiply(f1, f2)
print(f"Multiply {f1} by {f2} : {multiplyresult}")
divideresult = divide(f1, f2)
print(f"Divide {f1} by {f2} : {divideresult}")

Write a function convert_to_int_list(slist) that takes a list of strings and returns a list of integers. Call it on slist and print the result.

[1, 2, 3]

def convert_to_int_list(slist):
    ilist = []
    for x in slist:
        ilist.append(int(x))
    return ilist


print(convert_to_int_list(slist))

Write a function summate(ilist) that takes a list of integers and returns their sum. Replace the loop in the cell with a call to convert_to_int_list that gives intlist, and a call to summate that gives summation. The Average line at the bottom still uses summation. Run the cell.

Sum of list [1, 2, 3] is 6

def summate(ilist):
    s = 0
    for x in ilist:
        s = s + x
    return s


intlist = convert_to_int_list(slist)
summation = summate(intlist)
print(f"Sum of list {intlist} is {summation}")

Write a function average(ilist) that returns the mean of a list of integers, and replace the starter's line average = summation / len(intlist) with a call to it. Keep no variable named average, or it hides your function.

Average of list [1, 2, 3] is 2.0

def average(ilist):
    return summate(ilist) / len(ilist)


print(f"Average of list {intlist} is {average(intlist)}")

The starter printed Sum of list ['1', '2', '3'], with quotes. Yours does not. Write a comment that says why.

# The starter appended x to intlist before it was converted, so the list held strings.
# convert_to_int_list appends int(x), so the list holds numbers and prints without quotes.

Write a function faculty(n) that returns the factorial of n, which is n × (n-1) × (n-2) × ... × 1. The name is the one the rest of the course uses, from the Dutch faculteit. Write it recursively : the function calls itself with a smaller number. It returns 1 for 0 and for 1. Print faculty(5).

120

def faculty(n):
    if n == 0 or n == 1:
        return 1
    return n * faculty(n - 1)


print(faculty(5))

Call faculty(-1) inside a try that catches Exception as error, and print type(error).__name__ and the message of the error.

RecursionError maximum recursion depth exceeded

try:
    faculty(-1)
except Exception as error:
    print(type(error).__name__, error)

Make faculty refuse a negative number with a ValueError and a message that names the number. Call faculty(-1) inside a try and print the message.

faculty(-1) : no factorial for a negative number : -1

def faculty(n):
    if n < 0:
        raise ValueError(f"no factorial for a negative number : {n}")
    if n == 0 or n == 1:
        return 1
    return n * faculty(n - 1)


try:
    faculty(-1)
except ValueError as error:
    print("faculty(-1) :", error)

Call faculty(3000) inside a try that catches RecursionError, and print the message.

faculty(3000) : maximum recursion depth exceeded

try:
    faculty(3000)
except RecursionError as error:
    print("faculty(3000) :", error)