12.17. Exercises

1. Write a function named num_test that takes a number as input. If the number is greater than 10, the function should return “Greater than 10.” If the number is less than 10, the function should return “Less than 10.” If the number is equal to 10, the function should return “Equal to 10.”

   ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(num_test(5), "Less than 10.", "Testing the num_test function on input 5.") self.assertEqual(num_test(0), "Less than 10.", "Testing the num_test function on input 0.") self.assertEqual(num_test(12.99), "Greater than 10.", "Testing the num_test function on input 12.99.") self.assertEqual(num_test(10.00), "Equal to 10.", "Testing the num_test function on input 10.00.") myTests().main()

2. Write a function that will return the number of digits in an integer.

   def numDigits(n): # your code here ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(numDigits(2),1,"Tested numDigits on input of 2") self.assertEqual(numDigits(55),2,"Tested numDigits on input of 55") self.assertEqual(numDigits(1352),4,"Tested numDigits on input of 1352") self.assertEqual(numDigits(444),3,"Tested numDigits on input of 444") myTests().main()

   def numDigits(n): n_str = str(n) return len(n_str) print(numDigits(50)) print(numDigits(20000)) print(numDigits(1))

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3. Write a function that reverses its string argument.

   def reverse(astring): # your code here ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(reverse("happy"),"yppah","Tested reverse on input of 'happy'") self.assertEqual(reverse("Python"),"nohtyP","Tested reverse on input of 'Python'") self.assertEqual(reverse(""),"","Tested reverse on input of ''") myTests().main()

4. Write a function that mirrors its string argument, generating a string containing the original string and the string backwards.

   def mirror(mystr): # your code here ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(mirror("good"),"gooddoog","Tested mirror on input of 'good'") self.assertEqual(mirror("Python"),"PythonnohtyP","Tested mirror on input of 'Python'") self.assertEqual(mirror(""),"","Tested mirror on input of ''") self.assertEqual(mirror("a"),"aa","Tested mirror on input of 'a'") myTests().main()

   def reverse(mystr): reversed = '' for char in mystr: reversed = char + reversed return reversed def mirror(mystr): return mystr + reverse(mystr) assert mirror('good') == 'gooddoog' assert mirror('Python') == 'PythonnohtyP' assert mirror('') == '' assert mirror('a') == 'aa'

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5. Write a function that removes all occurrences of a given letter from a string.

   def remove_letter(theLetter, theString): # your code here ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(remove_letter("a","apple"),"pple","Tested remove_letter on inputs of 'a' and 'apple'") self.assertEqual(remove_letter("a","banana"),"bnn","Tested remove_letter on inputs of 'a' and 'banana'") self.assertEqual(remove_letter("z","banana"),"banana","Tested remove_letter on inputs of 'z' and 'banana'") myTests().main()

6. Although Python provides us with many list methods, it is good practice and very instructive to think about how they are implemented. Implement a Python function that works like the following:

   1. count

   2. in

   3. reverse

   4. index

   5. insert

   def count(obj, lst): count = 0 for e in lst: if e == obj: count = count + 1 return count def is_in(obj, lst): # cannot be called in() because in is a reserved keyword for e in lst: if e == obj: return True return False def reverse(lst): reversed = [] for i in range(len(lst)-1, -1, -1): # step through the original list backwards reversed.append(lst[i]) return reversed def index(obj, lst): for i in range(len(lst)): if lst[i] == obj: return i return -1 def insert(obj, index, lst): newlst = [] for i in range(len(lst)): if i == index: newlst.append(obj) newlst.append(lst[i]) return newlst lst = [0, 1, 1, 2, 2, 3, 4, 5, 6, 7, 8, 9] print(count(1, lst)) print(is_in(4, lst)) print(reverse(lst)) print(index(2, lst)) print(insert('cat', 4, lst))

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7. Write a function replace(s, old, new) that replaces all occurences of old with new in a string s:

   test(replace('Mississippi', 'i', 'I'), 'MIssIssIppI')
   
   s = 'I love spom!  Spom is my favorite food.  Spom, spom, spom, yum!'
   test(replace(s, 'om', 'am'),
          'I love spam!  Spam is my favorite food.  Spam, spam, spam, yum!')
   
   test(replace(s, 'o', 'a'),
          'I lave spam!  Spam is my favarite faad.  Spam, spam, spam, yum!')
   

   Hint: use the split and join methods.

   def replace(s, old, new): # your code here ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(replace('Mississippi','i','I'),'MIssIssIppI',"Tested replace on input 'Mississippi','i','I'") self.assertEqual(replace('Bookkeeper','e','A'),'BookkAApAr',"Tested failed on input 'Bookkeeper','e','A'") self.assertEqual(replace('Deeded','e','q'),'Dqqdqd',"Tested failed on input 'Deeded','e','q'") myTests().main()

8. Write a Python function that will take a the list of 100 random integers between 0 and 1000 and return the maximum value. (Note: there is a builtin function named max but pretend you cannot use it.)

   import random as r lst = [] for i in range(100): num = r.randint(1, 1000) lst.append(num) def largest(lst): #your code here ==== from unittest.gui import TestCaseGui import re class myTests(TestCaseGui): def testOne(self): output = self.getOutput().split('\n') editor = self.getEditorText().split('\n') float_re = r'[-+]?(\d+(\.\d*)?|\.\d+)([eE][-+]?\d+)?' self.assertEqual(largest(lst), max(lst), 'Checking for the list'+ str(lst)) # hardcode check self.assertFalse(re.search(r'max', self.getEditorText()), 'Checking for max') myTests().main()

   import random def max(lst): max = 0 for e in lst: if e > max: max = e return max lst = [] for i in range(100): lst.append(random.randint(0, 1000)) print(max(lst))

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9. Write a function sum_of_squares(xs) that computes the sum of the squares of the numbers in the list xs. For example, sum_of_squares([2, 3, 4]) should return 4+9+16 which is 29:

   def sum_of_squares(xs): # your code here ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(sum_of_squares([2,3,4]),29,"Tested sum_of_squares on input [2,3,4]") self.assertEqual(sum_of_squares([0,1,-1]),2,"Tested sum_of_squares on input [0,1,-1]") self.assertEqual(sum_of_squares([5,12,14]),365,"Tested sum_of_squares on input [5,12,14]") myTests().main()

10. Write a function to count how many odd numbers are in a list.

    def countOdd(lst): # your code here ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(countOdd([1,3,5,7,9]),5,"Tested countOdd on input [1,3,5,7,9]") self.assertEqual(countOdd([1,2,3,4,5]),3,"Tested countOdd on input [-1,-2,-3,-4,-5]") self.assertEqual(countOdd([2,4,6,8,10]),0,"Tested countOdd on input [2,4,6,8,10]") self.assertEqual(countOdd([0,-1,12,-33]),2,"Tested countOdd on input [0,-1,12,-33]") myTests().main()

    import random def countOdd(lst): odd = 0 for e in lst: if e % 2 != 0: odd = odd + 1 return odd # make a random list to test the function lst = [] for i in range(100): lst.append(random.randint(0, 1000)) print(countOdd(lst))

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11. Sum up all the even numbers in a list.

    def sumEven(lst): # your code here ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(sumEven([1,3,5,7,9]),0,"Tested sumEven on input [1,3,5,7,9]") self.assertEqual(sumEven([-1,-2,-3,-4,-5]),-6,"Tested sumEven on input [-1,-2,-3,-4,-5]") self.assertEqual(sumEven([2,4,6,7,9]),12,"Tested sumEven on input [2,4,6,7,9]") self.assertEqual(sumEven([0,1,12,33]),12,"Tested sumEven on input [0,1,12,33]") myTests().main()

12. Sum up all the negative numbers in a list.

    def sumNegatives(lst): # your code here ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(sumNegatives([-1,-2,-3,-4,-5]),-15,"Tested sumNegatives on input [-1,-2,-3,-4,-5]") self.assertEqual(sumNegatives([1,-3,5,-7,9]),-10,"Tested sumNegatives on input [1,-3,5,-7,9]") self.assertEqual(sumNegatives([-2,-4,6,-7,9]),-13,"Tested sumNegatives on input [-2,-4,6,-7,9]") self.assertEqual(sumNegatives([0,1,2,3,4]),0,"Tested sumNegatives on input [0,1,2,3,4]") myTests().main()

    import random def sumNegative(lst): sum = 0 for e in lst: if e < 0: sum = sum + e return sum lst = [] for i in range(100): lst.append(random.randrange(-1000, 1000)) print(sumNegative(lst))

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13. Write a function findHypot. The function will be given the length of two sides of a right-angled triangle and it should return the length of the hypotenuse. (Hint: x ** 0.5 will return the square root, or use sqrt from the math module)

    def findHypot(a,b): # your code here ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(findHypot(12.0,5.0),13.0,"Tested findHypot on inputs of 12.0 and 5.0") self.assertEqual(findHypot(14.0,48.0),50.0,"Tested findHypot on inputs of 14.0 and 48.0") self.assertEqual(findHypot(21.0,72.0),75.0,"Tested findHypot on inputs of 21.0 and 72.0") self.assertAlmostEqual(findHypot(1,1.73205),1.999999,2,"Tested findHypot on inputs of 1 and 1.73205") myTests().main()

14. Write a function called is_even(n) that takes an integer as an argument and returns True if the argument is an even number and False if it is odd.

    def is_even(n): #your code here ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(is_even(10),True,"Tested is_even on input of 10") self.assertEqual(is_even(5),False,"Tested is_even on input of 5") self.assertEqual(is_even(1),False,"Tested is_even on input of 1") self.assertEqual(is_even(0),True,"Tested is_even on input of 0") myTests().main()

15. Now write the function is_odd(n) that returns True when n is odd and False otherwise.

    def is_odd(n): # your code here ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(is_odd(10),False,"Tested is_odd on input of 10") self.assertEqual(is_odd(5),True,"Tested is_odd on input of 5") self.assertEqual(is_odd(1),True,"Tested is_odd on input of 1") self.assertEqual(is_odd(0),False,"Tested is_odd on input of 0") myTests().main()

16. Write a function is_rightangled which, given the length of three sides of a triangle, will determine whether the triangle is right-angled. Assume that the third argument to the function is always the longest side. It will return True if the triangle is right-angled, or False otherwise.

    Hint: floating point arithmetic is not always exactly accurate, so it is not safe to test floating point numbers for equality. If a good programmer wants to know whether x is equal or close enough to y, they would probably code it up as

    if  abs(x - y) < 0.001:      # if x is approximately equal to y
        ...
    

    def is_rightangled(a, b, c): # your code here ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(is_rightangled(1.5,2.0,2.5),True,"Tested is_rightangled on inputs of 1.5, 2.0 and 2.5") self.assertEqual(is_rightangled(4.0,8.0,16.0),False,"Tested is_rightangled on inputs of 4.0, 8.0 and 16.0") self.assertEqual(is_rightangled(4.1,8.2,9.1678787077),True,"Tested is_rightangled on inputs of 4.1, 8.2 and 9.1678787077") self.assertEqual(is_rightangled(4.1,8.2,9.16787),True,"Tested is_rightangled on inputs of 4.1, 8.2, and 9.16787") self.assertEqual(is_rightangled(4.1,8.2,9.168),False,"Tested is_rightangled on inputs of 4.1, 8.2 and 9.168") self.assertEqual(is_rightangled(0.5,0.4,0.64031),True,"Tested is_rightangled on inputs of 0.5, 0.4 and 0.64031") myTests().main()

12.17.1. Contributed Exercises

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