4.8. Exercises¶

In Robert McCloskey’s book Make Way for Ducklings, the names of the ducklings are Jack, Kack, Lack, Mack, Nack, Ouack, Pack, and Quack. This loop tries to output these names in order. Save your answer in a variable named words and make sure that this value doesn’t get overwritten later in your program.
```
prefixes = "JKLMNOPQ"
suffix = "ack"

words = [first + suffix for first in prefixes]
```
Of course, that’s not quite right because Ouack and Quack are misspelled. Can you fix it?

Write a function that will return the number of digits in an integer.
numDigits = lambda n: 0 # 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()
numDigits = lambda n: len(str(n)) print(numDigits(50)) print(numDigits(20000)) print(numDigits(1))

Write a function named reverse_str that reverses its string argument.
reverse = lambda astring: "a" # 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()

Write a function that takes a string and mirrors its argument. For example the mirror of "good" is "gooddoog".
mirror = lambda mystr: "abba" # 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()
reverse = lambda mystr: ''.join([ c for c in reversed(mystr)]) mirror = lambda mystr: mystr + reverse(mystr)

Write a function named remove_char that removes all occurrences of a given letter from a string. Do not use the replace string method.
remove_char = lambda theLetter, theString: "stuff" # your code here ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(remove_char("a","apple"),"pple","Tested remove_char on inputs of 'a' and 'apple'") self.assertEqual(remove_char("a","banana"),"bnn","Tested remove_char on inputs of 'a' and 'banana'") self.assertEqual(remove_char("z","banana"),"banana","Tested remove_char on inputs of 'z' and 'banana'") myTests().main()

Write a function that recognizes palindromes. (Hint: use your reverse function to make this easy!). Hint: Use all, reversed and zip.
is_palindrome lambda myStr: False # your code here ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(is_palindrome("abba"),True,"Tested is_palindrome on input of 'abba'") self.assertEqual(is_palindrome("abab"),False,"Tested is_palindrome on input of 'abab'") self.assertEqual(is_palindrome("straw warts"),True,"Tested is_palindrome on input of 'straw warts'") self.assertEqual(is_palindrome("a"),True,"Tested is_palindrome on input of 'a'") self.assertEqual(is_palindrome(""),True,"Tested is_palindrome on input of ''") myTests().main()
pairs = lambda mystr: [(i, j) for i, j in zip(mystr,reversed(mystr))] check_each_pair = lambda mypairs: [i == j for i, j in pairs] is_palindrome lambda myStr: all(check_each_pair(myStr)) # Or all together is_palindrome_alt = lambda s: all([i ==j for i, j in zip(s, reversed(s))])

Write a function that removes all occurrences of a string from another string. Do not use the remove string method in your solution.
remove_substring = lambda substr,s: 'code here' ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(remove_substring("an","banana"),"ba","Tested remove_all on inputs of 'an' and 'banana'") self.assertEqual(remove_substring("cyc","bicycle"),"bile","Tested remove_all on inputs of 'cyc' and 'bicycle'") self.assertEqual(remove_substring("iss","Mississippi"),"Mippi","Tested remove_all on inputs of 'iss' and 'Mississippi'") self.assertEqual(remove_substring("eggs","bicycle"),"bicycle","Tested remove_all on inputs of 'eggs' and 'bicycle'") myTests().main()

Create a list containing 100 random integers between 0 and 1000 (use iteration, a comprehension, and the random module). Write a function called average that will take the list as a parameter and return the average.

Write a Python function that takes n and m as input and returns the maximum value of a the list of n random integers between 0 and m. (Note:. there is a builtin function named max.)

from random import randint rand_max = lambda n, m: max([randint(0,m) for i in range(n)])

Write a function called mean_normal(n, m, sd) that computes the mean of n randomly selected values taken from a normal distribution with mean m and standard deviation sd.

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:
sum_of_squares = lambda xs: 1 # 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()

Write a function to count how many odd numbers are in a list.
countOdd = lambda lst: 3 # 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 countOdd = lambda lst: sum([1 for i in lst of i % 2 == 1]) # make a random list to test the function lst = [random.randint(0, 1000) for i in range(100)] print(countOdd(lst))

Write a function called sum_even that sums up all the even numbers in a list.
sum_even = lambda lst: 42 # your code here ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual(sum_even([1,3,5,7,9]),0,"Tested sum_even on input [1,3,5,7,9]") self.assertEqual(sum_even([-1,-2,-3,-4,-5]),-6,"Tested sum_even on input [-1,-2,-3,-4,-5]") self.assertEqual(sum_even([2,4,6,7,9]),12,"Tested sum_even on input [2,4,6,7,9]") self.assertEqual(sum_even([0,1,12,33]),12,"Tested sum_even on input [0,1,12,33]") myTests().main()

Sum up all the negative numbers in a list.
sumNegatives = lambda lst: -1 # 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 sumNegatives = lambda lst: sum([1 for i in lst if i < 0]) lst = [random.randint(0, 1000) for i in range(100)] print(sumNegative(lst))

Write a function called num_greater_5 that counts how many words in a list have length 5.
num_greater_5 = lambda lst: 23 # your code here

Use the function from the last problem to count how many words in Emma have length of at least 5. Save your result in a variable named num_words_emma.

Note: You should clean up such that
1. Hyphenated words count as separate words.
2. The words contracted with an apostrophe count as two words.

Create a function that takes a value n as input and constructs a multiplication table for whole numbers up to \(n\).

table = lambda n: [[i*j for i in range(1,n+1)] for j in range(1,n+1)] print(table(12))

Print out a neatly formatted multiplication table, up to 12 x 12. You should do this by constructing a string. For full credit, each column should be right-justified and your solution should include only comprehensions and lambda functions. Hint: Write a lambda function pads a number with the right number of spaces.

Use list comprehensions to filter the hours table to include only managers. In SQL this would be performed using SELECT and WHERE. Hint: Start by creating a list of the names of all managers. .. actex:: select-where

hours = [[“Alice”, 43],

[“Bob”, 37], [“Fred”, 15]]

titles = [[“Alice”, “Manager”],

[“Betty”, “Consultant”], [“Bob”, “Assistant”]]

Use list comprehensions to decide if the following tables contain a manager that worked at least 40 hours.
hours = [["Alice", 43], ["Bob", 37], ["Fred", 15]] titles = [["Alice", "Manager"], ["Betty", "Consultant"], ["Bob", "Assistant"]]

Use list comprehensions to perform a right outer join on the following lists.
hours = [["Alice", 43], ["Bob", 37], ["Fred", 15]] titles = [["Alice", "Manager"], ["Betty", "Consultant"], ["Bob", "Assistant"]]

Use a list comprehension and lambda expression to create a sequence of functions that combine to average two matrices. A complete solution will provide functions for each level of abstraction.
M1 = [[1, 2], [3, 4]] M2 = [[5, 6], [7, 8]]

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