46 Python exercises: 31-35!

31. Implement the higher order functions map(), filter() and reduce(). (They are built-in but writing them yourself may be a good exercise.)


32. Write a version of a palindrome recogniser that accepts a file name from the user, reads each line, and prints the line to the screen if it is a palindrome.



33. According to Wikipedia, a semordnilap is a word or phrase that spells a differentword or phrase backwards. (“Semordnilap” is itself “palindromes” spelled backwards.) Write a semordnilap recogniser that accepts a file name (pointing to a list of words) from the user and finds and prints all pairs of words that are semordnilaps to the screen. For example, if “stressed” and “desserts” is part of the word list, the the output should include the pair “stressed desserts”. Note, by the way, that each pair by itself forms a palindrome!


34. Write a procedure char_freq_table() that, when run in a terminal, accepts a file name from the user, builds a frequency listing of the characters contained in the file, and prints a sorted and nicely formatted character frequency table to the screen.



35. The International Civil Aviation Organization (ICAO) alphabet assigns code words to the letters of the English alphabet acrophonically (Alfa for A, Bravo for B, etc.) so that critical combinations of letters (and numbers) can be pronounced and understood by those who transmit and receive voice messages by radio or telephone regardless of their native language, especially when the safety of navigation or persons is essential. Here is a Python dictionary covering one version of the ICAO alphabet:

d = {'a':'alfa', 'b':'bravo', 'c':'charlie', 'd':'delta', 'e':'echo', 'f':'foxtrot',
     'g':'golf', 'h':'hotel', 'i':'india', 'j':'juliett', 'k':'kilo', 'l':'lima',
     'm':'mike', 'n':'november', 'o':'oscar', 'p':'papa', 'q':'quebec', 'r':'romeo',
     's':'sierra', 't':'tango', 'u':'uniform', 'v':'victor', 'w':'whiskey', 
     'x':'x-ray', 'y':'yankee', 'z':'zulu'}

Your task in this exercise is to write a procedure speak_ICAO() able to translate any text (i.e. any string) into spoken ICAO words. You need to import at least two libraries: os and time. On a mac, you have access to the system TTS (Text-To-Speech) as follows: os.system(‘say ‘ + msg), where msg is the string to be spoken. (Under UNIX/Linux and Windows, something similar might exist.) Apart from the text to be spoken, your procedure also needs to accept two additional parameters: a float indicating the length of the pause between each spoken ICAO word, and a float indicating the length of the pause between each word spoken.EJ35


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