Exercises¶

1. • Question
   • Answer

   What is the result of each of the following:

   1. ‘Python’[1]
   2. “Strings are sequences of characters.”[5]
   3. len(“wonderful”)
   4. ‘Mystery’[:4]
   5. ‘p’ in ‘Pineapple’
   6. ‘apple’ in ‘Pineapple’
   7. ‘pear’ not in ‘Pineapple’
   8. ‘apple’ > ‘pineapple’
   9. ‘pineapple’ < ‘Peach’

   1. ‘Python’[1] = ‘y’
   2. ‘Strings are sequences of characters.’[5] = ‘g’
   3. len(‘wonderful’) = 9
   4. ‘Mystery’[:4] = ‘Myst’
   5. ‘p’ in ‘Pineapple’ = True
   6. ‘apple’ in ‘Pineapple’ = True
   7. ‘pear’ not in ‘Pineapple’ = True
   8. ‘apple’ > ‘pineapple’ = False
   9. ‘pineapple’ < ‘Peach’ = False
2. • Question
   • Answer

   Assign to a variable in your program a triple-quoted string that contains your favorite paragraph of text - perhaps a poem, a speech, instructions to bake a cake, some inspirational verses, etc.

   Write a function that counts the number of alphabetic characters (a through z, or A through Z) in your text and then keeps track of how many are the letter ‘e’. Your function should print an analysis of the text like this:

   Your text contains 243 alphabetic characters, of which 109 (44.8%) are 'e'.
   

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   (ex_8_3)

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   def count(p): lows = "abcdefghijklmnopqrstuvwxyz" ups = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" numberOfe = 0 totalChars = 0 for achar in p: if achar in lows or achar in ups: totalChars = totalChars + 1 if achar == 'e': numberOfe = numberOfe + 1 percent_with_e = (numberOfe / totalChars) * 100 print("Your text contains", totalChars, "alphabetic characters of which", numberOfe, "(", percent_with_e, "%)", "are 'e'.") p = ''' "If the automobile had followed the same development cycle as the computer, a Rolls-Royce would today cost $100, get a million miles per gallon, and explode once a year, killing everyone inside." -Robert Cringely ''' count(p)

   (q3_answer)

3. • Question
   • Answer

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

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   (ex_7_10)

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

   (q5_answer)

4. Write a function that reverses its string argument.

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   from test import testEqual def reverse(astring): # your code here testEqual(reverse("happy"), "yppah") testEqual(reverse("Python"), "nohtyP") testEqual(reverse(""), "")

   (ex_8_5)

5. • Question
   • Answer

   Write a function that mirrors its argument.

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   from test import testEqual def mirror(mystr): # your code here testEqual(mirror('good'), 'gooddoog') testEqual(mirror('Python'), 'PythonnohtyP') testEqual(mirror(''), '') testEqual(mirror('a'), 'aa')

   (ex_8_6)

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   from test import testEqual def reverse(mystr): reversed = '' for char in mystr: reversed = char + reversed return reversed def mirror(mystr): return mystr + reverse(mystr) testEqual(mirror('good'), 'gooddoog') testEqual(mirror('Python'), 'PythonnohtyP') testEqual(mirror(''), '') testEqual(mirror('a'), 'aa')

   (q7_answer)

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

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   from test import testEqual def remove_letter(theLetter, theString): # your code here testEqual(remove_letter('a', 'apple'), 'pple') testEqual(remove_letter('a', 'banana'), 'bnn') testEqual(remove_letter('z', 'banana'), 'banana')

   (ex_8_7)

7. • Question
   • Answer

   Write a function that recognizes palindromes. (Hint: use your reverse function to make this easy!).

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   from test import testEqual def is_palindrome(myStr): # your code here testEqual(is_palindrome('abba'), True) testEqual(is_palindrome('abab'), False) testEqual(is_palindrome('straw warts'), True) testEqual(is_palindrome('a'), True) testEqual(is_palindrome(''), True)

   (ex_8_8)

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   from test import testEqual def reverse(mystr): reversed = '' for char in mystr: reversed = char + reversed return reversed def is_palindrome(myStr): if myStr in reverse(myStr): return True else: return False testEqual(is_palindrome('abba'), True) testEqual(is_palindrome('abab'), False) testEqual(is_palindrome('straw warts'), True) testEqual(is_palindrome('a'), True) testEqual(is_palindrome(''), True)

   (q9_answer)

8. Write a function that counts how many times a substring occurs in a string.

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   from test import testEqual def count(substr,theStr): # your code here testEqual(count('is', 'Mississippi'), 2) testEqual(count('an', 'banana'), 2) testEqual(count('ana', 'banana'), 2) testEqual(count('nana', 'banana'), 1) testEqual(count('nanan', 'banana'), 0) testEqual(count('aaa', 'aaaaaa'), 4)

   (ex_8_9)

9. • Question
   • Answer

   Write a function that removes the first occurrence of a string from another string.

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   from test import testEqual def remove(substr,theStr): # your code here testEqual(remove('an', 'banana'), 'bana') testEqual(remove('cyc', 'bicycle'), 'bile') testEqual(remove('iss', 'Mississippi'), 'Missippi') testEqual(remove('egg', 'bicycle'), 'bicycle')

   (ex_8_10)

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   from test import testEqual def remove(substr,theStr): index = theStr.find(substr) if index < 0: # substr doesn't exist in theStr return theStr return_str = theStr[:index] + theStr[index+len(substr):] return return_str testEqual(remove('an', 'banana'), 'bana') testEqual(remove('cyc', 'bicycle'), 'bile') testEqual(remove('iss', 'Mississippi'), 'Missippi') testEqual(remove('egg', 'bicycle'), 'bicycle')

   (q11_answer)

10. Write a function that removes all occurrences of a string from another string.

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    from test import testEqual def remove_all(substr,theStr): # your code here testEqual(remove_all('an', 'banana'), 'ba') testEqual(remove_all('cyc', 'bicycle'), 'bile') testEqual(remove_all('iss', 'Mississippi'), 'Mippi') testEqual(remove_all('eggs', 'bicycle'), 'bicycle')

    (ex_8_11)

11. Write a function called removeDups that takes a string and creates a new string by only adding those characters that are not already present. In other words, there will never be a duplicate letter added to the new string.

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    def removeDups(astring): # your code here print(removeDups("mississippi")) #should print misp

    (ex_8_19)