15.6. Exercises

21. 1. Fill in the parameter list for g so that the invocations of g yield the return values specified

    def g(): return 2*x + y + z print(g(3)) # should output 10 print(g(3, 2)) # should output 8 print(g(3, 2, 1)) #should output 9

22. 2. Define a function called nums that has three parameters. The first parameter, an integer, should be required. A second parameter named mult_int should be optional with a default value of 5. The final parameter, switch, should also be optional with a default value of False. The function should multiply the two integers together, and if switch is True, should change the sign of the product before returning it.

    def nums(): pass #remove this once you start writing the function ===== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(nums(5), 25, "Testing the function nums on input 5.") self.assertEqual(nums(2, mult_int = 4), 8, "Testing the function nums on inputs 2, mult_int = 4.") self.assertEqual(nums(3, switch = True), -15, "Testing the function nums on inputs 3, switch = True.") self.assertEqual(nums(4, mult_int = 3, switch = True), -12, "Testing the function nums on inputs 4, mult_int = 3, switch = True.") self.assertEqual(nums(0, switch = True), 0, "Testing the function nums on inputs 0, switch = True.") myTests().main()

23. 3. Write a function called together that takes three parameters, the first is a required parameter that is a number (integer or float), the second is a required parameter that is a string, and the third is an optional parameter whose default is ” “. What is returned is the first parameter, concatenated with the second, using the third.

    ===== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(together(12, 'cats'), '12 cats', "Testing that together returns the correct string on input (12, 'cats')") self.assertEqual(together(17.3, 'birthday cakes'), '17.3 birthday cakes', "Testing that together returns the correct string on input (17.3, 'birthday cakes')") self.assertEqual(together(3, 'dogs', ': '), '3: dogs', "Testing that together returns the correct string on input (3, 'dogs', ': ')") self.assertEqual(together(493.3, 'beans', ' lima '), '493.3 lima beans', "Testing that together returns the correct string on input (493.3, 'beans', 'lima')") myTests().main()

15.6.1. Contributed Exercises

Q-1: After completing the reading, what concepts are still unclear to you? If nothing is unclear, what did you find most interesting?

Write a function named add_wvu(). It should accept one parameter, an optional parameter named colleges designed to take a list. If an existing list is not provided for colleges when calling your function, your function should create a new list.

Your function must append an entry containing “WVU” to the colleges list, and return the updated list.

Be careful that if add_wvu() is called multiple times, any lists it generates are new and independent from other previously returned lists.

====

Create a lambda function that is designed to manipulate a dictionary, such as by returning the keys or values. Store the lambda function as lambda_func.

campuses = {'WVU Main Campus': 'Morgantown', 'Potomac State College' : 'Keyser', 'WVU Institute of Technology': 'Beckley'} lambda_func = # write your lambda function here print(lambda_func(campuses)) ====

Create a function intadd that accepts two integers x and y. The first integer x should have a default value of 7 and the second integer y should have a default value of 3. The function should add the two integers and return this value.

==== from unittest.gui import TestCaseGui import re class myTests(TestCaseGui): def testOne(self): self.assertTrue('def' in self.getEditorText(), 'function created') self.assertTrue(intadd(3,4)==7, '1st situation checked') self.assertTrue(intadd(3)==6, '2nd situation checked') self.assertTrue(intadd(y=4)==11, '3rd situation checked') myTests().main()

Q-1: Given the following sequence of stack operations, what is the top item on the stack when the sequence is complete?

m = Stack()
m.push('x')
m.push('y')
m.push('z')
while not m.isEmpty():
    m.pop()
    m.pop()

• 'x'
• You may want to check out the docs for isEmpty
• the stack is empty
• There is an odd number of things on the stack but each time through the loop 2 things are popped.
• an error will occur
• Good Job.
• 'z'
• You may want to check out the docs for isEmpty

Below is a program that simulates the rolling of dice. Modify this code and use it to simulate the 100 rolls of 5, 10 sided dice. Store the average roll in a variable called solution rounded to the nearest integer.

import random random.seed(3) def initialize(num_dice, n_sides=6): d={} for i in range(num_dice): d[i+1] = n_sides return d def roll(d, nrolls=1): result = 0 for die, sides in d.items(): result += random.randint(1,sides) return result def get_average(values): pass def main(): solution = 0 dice = initialize(2) print(roll(dice)) return solution solution = main() ===== from unittest.gui import TestCaseGui def result_hider(a, b): if a == b: return True class myTests(TestCaseGui): def testOne(self): self.assertEqual(result_hider(27, solution), True, "Testing") myTests().main()

Problem 1: Write a recursive function count(num, n) where num is a positive integer and n is a integer from 0 to 9. count returns the number of times the digit n is found in num. You should not have for or while loops in your code. Hint: The mod and the integer divide are your friends…

count(9983, 9)  # returns 2
count(9983, 0)  # returns 0

def count(num, n): # write your code here # Make your own test cases here ==== import re import sys from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): # hide print() fname = "test.out" sys.stdout = open(fname, "w") editText = self.getEditorText() numForWhile = len(re.findall("\s*while[( ]", editText)) + len(re.findall("\s*for ", editText)) if numForWhile > 0: self.assertEqual(numForWhile, 0, "Used a for or while in code") return # Make an object self.assertEqual(count(323123, 3), 3, "Testing count") self.assertEqual(count(923123, 9), 1, "Testing count") self.assertEqual(count(323120, 0), 1, "Testing count") self.assertEqual(count(123456, 7), 0, "Testing count") myTests().main()

Write a recursive function factorial(num) that given a number num, returns the factorial num!. For example, factorial(5) should return 120.

Hint: num! = num * (num - 1)!

def factorial(num): # write your code here print(factorial(5)) ==== import re from unittest.gui import TestCaseGui class myTests(TestCaseGui): def _factorial(self, num): if num<=1: return num return num * factorial(num-1) def testOne(self): SelfTest = False if (SelfTest): self.assertEqual(0,1,"Auto-testing if OFF - you must check the program yourself for now") return print('Auto-testing...') editText = self.getEditorText() self.assertEqual(0, len(re.findall("\s*while[( ]", editText)), "Should use no 'while' loops") self.assertEqual(0, len(re.findall("\s*for ", editText)), "Should use no 'for' loops") tests = [ 5, 8 ] for t in tests: self.assertEqual(factorial(t), self._factorial(t), 'Testing factorial({})'.format(t) ) myTests().main()

Write a recursive function palindrome(s) which takes a string s and returns True if the string is a palindrome, False otherwise. Ignore spaces and upper vs. lower case. You should not have for or while loops in your code.

def palindrome(s): # write your code here # Make your own test cases here ==== import sys import re from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): # hide print() fname = "test.out" sys.stdout = open(fname, "w") editText = self.getEditorText() numForWhile = len(re.findall("\s*while[( ]", editText)) + len(re.findall("\s*for ", editText)) if numForWhile > 0: self.assertEqual(numForWhile, 0, "Used a for or while in code") return # Make an object self.assertEqual(palindrome("kayak"), True, "Testing 'kayak'") self.assertEqual(palindrome("hurrah"), False, "Testing 'hurrah'") self.assertEqual(palindrome("abccba"), True, "Testing 'abccba'") self.assertEqual(palindrome("a"), True, "Testing 'a'") self.assertEqual(palindrome("Was it a car or a cat I saw"), True, "Testing 'Was it a car or a cat I saw'.\nNeed to ignore spaces and not case sensitive!") myTests().main()

Write a recursive function reverse(word) that given a string word, returns the reverse of word. For example, reverse('python') should return nohtyp.

Hint: Take the first character, reverse the remaining characters in the word, and concatenate the first character to the end of the new reversed string.

def reverse(word): # Your recursive code here print(reverse('python')) ==== import re from unittest.gui import TestCaseGui class myTests(TestCaseGui): def _reverse(self, word): if len(word)<=1: return word return reverse(word[1:]) + word[0] def testOne(self): SelfTest = False if (SelfTest): self.assertEqual(0,1,"Auto-testing if OFF - you must check the program yourself for now") return print('Auto-testing...') editText = self.getEditorText() self.assertEqual(0, len(re.findall("\s*while[( ]", editText)), "Should use no 'while' loops") self.assertEqual(0, len(re.findall("\s*for ", editText)), "Should use no 'for' loops") tests = [ 'python', 'computer', 'Angelo', '', 'A' ] for t in tests: self.assertEqual(reverse(t), self._reverse(t), 'Testing reverse(\'{}\')'.format(t) ) myTests().main()

The function whose code appears in the previous problem returns the index of the last occurrence of the parameter item in the list mylist, returning -1 if it is not found.

Order and indent the lines below so that they form a recursive equivalent of that function.

        def last_index(item, mylist):
---
    if len(mylist) == 0:
---
        return -1
---
    if mylist[-1] == item:
---
        return len(mylist) - 1
---
    return last_index(item, mylist[:-1])
        

Q-1: What is the runtime of the following code:

for i in range(n):
    if i % 2 == 0:
        new_vals[i] = old_vals[i] * i

• O(1)
• O(log n)
• O(n)
• O(n log n)
• O(n^2)

Q-1: What is the runtime of the following code:

val = n
count = 0
while val > 0:
    val = val // 2
    count += 1

• O(1)
• O(log n)
• O(n)
• O(n^2)
• O(n^3)

Q-1: This is not an actual problem. The code here will be referred to in the next problem. This “question” is worth 0 points, so select any answer (but only ‘a’ will get marked correct).

The function below returns the index of the last occurrence of the parameter item in the list mylist, returning -1 if it is not found. You will refer to this code in the next problem.

def last_index(item, mylist):
    for i in range(len(mylist) - 1, -1, -1):
        if mylist[i] == item:
            return i
    return -1

• I'm correct
• I'm incorrect
• I'm incorrect
• I'm incorrect

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